Body-worn vital sign monitor

ABSTRACT

The invention provides a body-worn vital sign monitor that measures a patient&#39;s vital signs (e.g. blood pressure, SpO2, heart rate, respiratory rate, and temperature) while simultaneously characterizing their activity state (e.g. resting, walking, convulsing, falling) and posture (upright, supine). The monitor processes this information to minimize corruption of the vital signs and associated alarms/alerts by motion-related artifacts. It also features a graphical user interface (GUI) rendered on a touchpanel display that facilitates a number of features to simplify and improve patient monitoring and safety in both the hospital and home.

CROSS REFERENCES TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/312,624, filed Mar. 10, 2010, entitled “BODY-WORN VITAL SIGNMONITOR”, which is incorporated herein in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to medical devices for monitoring vitalsigns, e.g., arterial blood pressure.

2. Description of the Related Art

Conventional vital sign monitors are used throughout the hospital, andare particularly commonplace in high-acuity areas such as the intensivecare unit (ICU), emergency department (ED), or operating room (OR).Patients in these areas are generally sick and require a high degree ofmedical attention, typically provided by a relatively high ratio ofclinicians compared to lower-acuity areas of the hospital. Outside theICU and OR, clinicians typically measure vital signs such as systolic,diastolic, and mean arterial blood pressures (SYS, DIA, MAP),respiratory rate (RR), oxygen saturation (SpO2), heart rate (HR), andtemperature (TEMP) with portable or wall-mounted vital sign monitors. Itcan be difficult to effectively monitor patients in this way, however,because measurements are typically made every few hours, and thepatients are often ambulatory and not constrained to a single hospitalroom. This poses a problem for conventional vital sign monitors, whichare typically heavy and unwieldy, as they are not intended for theambulatory population. To make a measurement, a patient is typicallytethered to the monitor with a series of tubes and wires. Some companieshave developed ambulatory vital sign monitors with limited capabilities(e.g. cuff-based blood pressure using oscillometry and SpO2 monitoring),but typically these devices only make intermittent, rather thancontinuous, measurements. And even these measurements tend to work beston stationary patients, as they are easily corrupted by motion-relatedartifacts.

Most vital signs monitors feature a user interface that shows numericalvalues and waveforms associated with the vital signs, alarm parameters,and a ‘service menu’ that can be used to calibrate and maintain themonitor. Some monitors have internal wireless cards that communicatewith a hospital network, typically using protocols such as 802.11b/g.

One of the most important parameters measured with vital signs monitorsis blood pressure. In critical care environments like the ICU and OR,blood pressure can be continuously monitored with an arterial catheterinserted in the patient's radial or femoral artery. Alternatively, bloodpressure can be measured intermittently with a cuff using oscillometry,or manually by a clinician using auscultation. Most vital sign monitorsperform both catheter and cuff-based measurements of blood pressure.Blood pressure can also be monitored continuously with a techniquecalled pulse transit time (PTT), defined as the transit time for apressure pulse launched by a heartbeat in a patient's arterial system.PTT has been shown in a number of studies to correlate to SYS, DIA, andMAP. In these studies, PTT is typically measured with a conventionalvital signs monitor that includes separate modules to determine both anelectrocardiogram (ECG) and SpO2. During a PTT measurement, multipleelectrodes typically attach to a patient's chest to determine atime-dependent ECG component characterized by a sharp spike called the‘QRS complex’. The QRS complex indicates an initial depolarization ofventricles within the heart and, informally, marks the beginning of theheartbeat and a pressure pulse that follows.

SpO2 is typically measured with a bandage or clothespin-shaped sensorthat clips to a patient's finger and includes optical systems operatingin both the red and infrared spectral regions. A photodetector measuresradiation emitted from the optical systems that transmits through thepatient's finger. Other body sites, e.g., the ear, forehead, and nose,can also be used in place of the finger. During a measurement, amicroprocessor analyses both red and infrared radiation detected by thephotodetector to determine the patient's blood oxygen saturation leveland a time-dependent waveform called a photoplethysmograph (PPG).Time-dependent features of the PPG indicate both pulse rate and avolumetric absorbance change in an underlying artery caused by thepropagating pressure pulse.

Typical PTT measurements determine the time separating a maximum pointon the QRS complex (indicating the peak of ventricular depolarization)and a foot of the PPG waveform (indicating the beginning the pressurepulse). PTT depends primarily on arterial compliance, the propagationdistance of the pressure pulse (which is closely approximated by thepatient's arm length), and blood pressure. To account forpatient-dependent properties, such as arterial compliance, PTT-basedmeasurements of blood pressure are typically ‘calibrated’ using aconventional blood pressure cuff and oscillometry. Typically during thecalibration process the blood pressure cuff is applied to the patient,used to make one or more blood pressure measurements, and then left forfuture measurements. Going forward, the calibration measurements areused, along with a change in PTT, to measure the patient's continuousblood pressure (cNIBP). PTT typically relates inversely to bloodpressure, i.e., a decrease in PTT indicates an increase in bloodpressure.

A number of issued U.S. patents describe the relationship between PTTand blood pressure. For example, U.S. Pat. Nos. 5,316,008; 5,857,975;5,865,755; and 5,649,543 each describe an apparatus that includesconventional sensors that measure both ECG and PPG waveforms which arethen processed to determine PTT.

SUMMARY OF THE INVENTION

To improve the safety of hospitalized patients, particularly those inlower-acuity areas, it is desirable to have a body-worn monitor thatcontinuously measures all vital signs from a patient, provides tools foreffectively monitoring the patient, and wirelessly communicates with ahospital's information technology (IT) network. Preferably the monitoroperates algorithms featuring: 1) a low percentage of false positivealarms/alerts; and 2) a high percentage of true positive alarms/alerts.The term ‘alarm/alert’, as used herein, refers to an audio and/or visualalarm generated directly by a monitor worn on the patient's body, oralternatively a remote monitor (e.g., a central nursing station). Toaccomplish this, the invention provides a body-worn monitor thatmeasures a patient's vital signs (e.g. cNIBP, SpO2, HR, RR, and TEMP)while simultaneously characterizing their activity state (e.g. resting,walking, convulsing, falling) and posture (upright, supine). Thebody-worn monitor processes this information to minimize corruption ofthe vital signs and associated alarms/alerts by motion-relatedartifacts.

The body-worn monitor features a graphical user interface (GUI) renderedon a touchpanel display that facilitates a number of features tosimplify and improve patient monitoring and safety in both the hospitaland home. For example, the monitor features a battery-powered,wrist-worn transceiver that processes motion-related signals generatedwith an internal motion sensor (e.g. an accelerometer). When thetransceiver's battery runs low, the entire unit can be swapped out bysimply ‘bumping’ the original transceiver with a new one having a fullycharged battery. Accelerometers within the transceivers detect the‘bump’, digitize the corresponding signals, and wirelessly transmit themto a patient data server (PDS) within the hospital's network. There, thesignals are analyzed and patient information (e.g. demographic and vitalsign data) formerly associated with the original transceiver isre-associated with the new transceiver. A clinician can view the datausing a computer functioning as a remote viewing device (RVD), such as aconventional computer on wheels (COW).

The body-worn monitor additionally includes a speaker, microphone, andsoftware that collectively facilitate voice over IP (VOIP)communication. With these features, the wrist-worn transceiver can beused as a two-way communicator allowing, e.g., the patient to alert aclinician during a time of need. Additionally, during medical proceduresor diagnoses, the clinician can enunciate annotations directly into thetransceiver. These annotations along with vital sign information arewirelessly transmitted to the PDS and ultimately a hospital's electronicmedical records (EMR) system, where they are stored and used forpost-hoc analysis of the patient. In a related application, thetransceiver includes a barcode scanner that, prior to administeringmedications, scans barcodes associated with the patient, clinician, andmedications. The transceiver sends the decoded barcode information backto the PDS, where a software program analyzes it to determine that thereare no errors in the medication or the rate at which it is delivered. Asignal is then sent from the PDS to the GUI, clearing the clinician toadminister the medications.

The body-worn monitor can determine a patient's location in addition totheir vital signs and motion-related properties. Typically, thelocation-determining sensor and the wireless transceiver operate on acommon wireless system, e.g. a wireless system based on 802.11a/b/g/n,802.15.4, or cellular protocols. In this case a location is determinedby processing the wireless signal with one or more algorithms known inthe art. These include, for example, triangulating signals received fromat least three different wireless base stations, or simply estimating alocation based on signal strength and proximity to a particular basestation. In still other embodiments the location sensor includes aconventional global positioning system (GPS).

VOIP-based communications typically take place between the body-wornmonitor and a remote computer or telephone interfaced to the PDS. Thelocation sensor, wireless transceiver, and first and second voiceinterfaces can all operate on a common wireless system, such as one ofthe above-described systems based on 802.11 or cellular protocols. Inembodiments, the remote computer, for example, can be a monitor that isessentially identical to the transceiver worn by the patient, and can becarried or worn by a clinician. In this case the monitor associated withthe clinician features a display wherein the user can select to displayinformation (e.g. vital signs, location, and alarms) corresponding to aparticular patient. This monitor can also include a voice interface sothe clinician can communicate with the patient.

The wrist-worn transceiver's touchpanel display can render a variety ofdifferent GUIs that query the patient for their pain level, test theirdegree of ‘mentation’, i.e. mental activity, and perform other functionsto assist and improve diagnosis. Additionally, the transceiver supportsother GUIs that allow the patient to order food within the hospital,change the channel on their television, select entertainment content,play games, etc. To help promote safety in the hospital, the GUI canalso render a photograph or video of the patient or, in the case ofneo-natal patients, their family members.

The body-worn monitor can include a software framework that generatesalarms/alerts based on threshold values that are either preset ordetermined in real time. The framework additionally includes a series of‘heuristic’ rules that take the patient's activity state and motion intoaccount, and process the vital signs accordingly. These rules, forexample, indicate that a walking patient is likely breathing and has aregular heart rate, even if their motion-corrupted vital signs suggestotherwise.

The body-worn monitor features a series of sensors that attach to thepatient to measure time-dependent PPG, ECG, ACC, oscillometric (OSC),and impedance pneumography (IP) waveforms. A microprocessor (CPU) withinthe monitor continuously processes these waveforms to determine thepatient's vital signs, degree of motion, posture and activity level.Sensors that measure these signals typically send digitized informationto the wrist-worn transceiver through a serial interface, or bus,operating on a controlled area network (CAN) protocol. The CAN bus istypically used in the automotive industry, and allows differentelectronic systems to effectively and robustly communicate with eachother with a small number of dropped packets, even in the presence ofelectrically noisy environments. This is particularly advantageous forambulatory patients that may generate signals with large amounts ofmotion-induced noise.

Blood pressure is determined continuously and non-invasively using atechnique, based on PTT, which does not require any source for externalcalibration. This technique, referred to herein as the ‘CompositeTechnique’, determines blood pressure using PPG, ECG, and OSC waveforms.The Composite Technique is described in detail in the co-pending patentapplication, the contents of which are fully incorporated herein byreference: BODY-WORN SYSTEM FOR MEASURING CONTINUOUS NON-INVASIVE BLOODPRESSURE (CNIBP) (U.S. Ser. No. 12/650, 354; filed Nov. 15, 2009). Inother embodiments, PTT can be calculated from time-dependent waveformsother than the ECG and PPG, and then processed to determine bloodpressure. In general, PTT can be calculated by measuring a temporalseparation between features in two or more time-dependent waveformsmeasured from the human body. For example, PTT can be calculated fromtwo separate PPGs measured by different optical sensors disposed on thepatient's fingers, wrist, arm, chest, ear, or virtually any otherlocation where an optical signal can be measured using a transmission orreflection-mode optical configuration. In other embodiments, PTT can becalculated using at least one time-dependent waveform measured with anacoustic sensor, typically disposed on the patient's chest. Or it can becalculated using at least one time-dependent waveform measured using apressure sensor, typically disposed on the patient's bicep, wrist, orfinger. The pressure sensor can include, for example, a pressuretransducer, piezoelectric sensor, actuator, polymer material, orinflatable cuff.

Specifically, in one aspect, the invention provides a method formonitoring a patient featuring the following steps: (a) associating afirst set of vital sign information measured from the patient with afirst transceiver that includes a first motion sensor; (b) storing thefirst set of vital sign information in a computer memory; (c) contactingthe first transceiver with a second transceiver that includes a secondmotion sensor, the contacting causing the first motion sensor togenerate a first motion signal and the second motion sensor to generatea second motion signal; (d) processing the first and second motionsignals to determine that the first transceiver is to be replaced by thesecond transceiver; and (e) associating a second set of vital signinformation with the patient, the second set of vital sign informationmeasured with the second transceiver.

In embodiments, both the first and second motion sensors areaccelerometers that generate time-dependent waveforms (e.g. ACCwaveforms). Contacting the two transceivers typically generateswaveforms that include individual ‘pulses’ (e.g. a sharp spike) causedby rapid acceleration and deceleration detected by the respectiveaccelerometers. Typically the pulses are within waveforms generatedalong the same axes in both transceivers. The pulses can be collectivelyprocessed (using, e.g., an autocorrelation algorithm) to determine thatthey are generated during a common period of time. In embodiments,amplitudes of the first and second pulses are required to exceed apre-determined threshold value in order for the second transceiver toreplace the first transceiver. Pulses that meet this criterion arewirelessly transmitted to a remote server, where they are processed asdescribed above. If the server determines that the second transceiver isready to replace the first transceiver, it transmits instructioninformation to the transceivers to guide the replacement process. Thisinstruction information, for example, is displayed by the GUIs of bothtransceivers. Once the replacement process is complete, vital signinformation measured by the second transceiver is stored along with thatmeasured by the first transceiver in a computer memory (e.g. a database)on the remote computer. The vital sign information can includeconventional vital signs (e.g. HR, SYS, DIA, RR, and TEMP), along withthe time-dependent waveforms used to calculate the vital signs (e.g.PPG, ECG, OSC, IP) and motion-related properties (ACC). Patientdemographic information (e.g. name, gender, weight, height, date ofbirth) can also be associated with both the first and second sets ofvital sign information.

In another aspect, the invention provides a method for pairing a patientmonitor with a remote display device (e.g. an RVD) using a methodologysimilar to that described above. The display device is typically aportable display device (e.g. a personal digital assistant, or PDA), ora remote computer, such as a COW or central nursing station. The methodincludes the following steps: (a) contacting either a display device oran area proximal to the display device with the transceiver to generatea motion signal with its internal accelerometer; (b) transmitting themotion signal to a computer; (c) processing the motion signal with thecomputer to associate the transceiver with the display device; (d)measuring a set of vital sign information from the patient with thetransceiver; and (e) displaying the set of vital sign information on thedisplay device. Here, the act of contacting the display device with thetransceiver generates a pulse in the ACC waveform, as described above.Processing done by the computer analyzes both the pulse and a locationof the display device to associate it with the transceiver.

Several methods can be used to determine the location of the displaydevice. For example, the wireless transmitter within the transceiver isconfigured to operate on a wireless network, and algorithms operating onthe remote computer and can analyze signals between the transceiver andwireless access points within the network (e.g. RSSI signals indicatingsignal strength) to determine an approximate location of the transceiverand thus the display device which it contacts. In embodiments thealgorithms can involve, e.g., triangulating at least three RSSI values,or simply estimating location by determining the nearest access pointfrom a single RSSI value. Triangulation typically involves using a mapgrid that includes known locations of multiple wireless access pointsand display devices within a region of the hospital; the map grid isdetermined beforehand and typically stored, e.g., in a database. Forexample, the approximate location of the transceiver can be determinedusing triangulation. Then the nearest display device, lying with a knownlocation within a pre-determined radius, is paired with the transceiver.Typically the pre-determined radius is between 1-5 m.

In another aspect, the invention provides a body-worn monitor includingfirst and second sensors attached to the patient, and a processingcomponent that interfaces to both sensors and processes signals fromthem to calculate at least one vital sign value. A wireless transmitterreceives the vital sign value and transmits it over a wirelessinterface, and additionally provides a two-way communications systemconfigured to transmit and receive audio signals over the same wirelessinterface. In embodiments, the two-way communications system includes aspeaker and a microphone, both of which are integrated into thetransceiver. Typically the wireless interface is a hospital-basedwireless network using an 802.11 protocol (e.g. 802.11a/b/g/n). A VOIPsystem typically runs on the wireless network to supply two-way voicecommunications. Alternatively the wireless network is based on acellular protocol, such as a GSM or CDMA protocol.

Typically the body-worn monitor features a wrist-worn transceiver thatfunctions as a processing component, and includes a touchpanel displayconfigured to render both patient and clinician interfaces. Thetouchpanel display is typically a liquid crystal display (LCD) ororganic light-emitting diode display (OLED) display with a cleartouchpanel utilizing established resistive or capacitive technologiesadhered to its front surface. The patient interface is typicallyrendered by default, and includes a graphical icon that, when initiated,activates the two-way communications system. The clinician interfacetypically requires a security code (entered using either a ‘soft’numerical keypad or through a barcode scanner) to be activated. Thetransceiver typically includes a strap configured to wrap around thepatient's arm, and most typically the wrist; this allows it to be wornlike a conventional wristwatch, which is ideal for two-waycommunications between the patient and a clinician.

In a related aspect, the invention provides a wrist-worn transceiverwherein the two-way communications system described above, or a versionthereof, is used as a voice annotation system. Such a system receivesaudio signals (typically from a clinician), digitizes them, andtransmits the resulting digital audio signals, or a set of parametersdetermined from these signals, over the wireless interface to a computermemory. The audio signals are typically used to annotate vital signinformation. They can be used, for example, to indicate when apharmaceutical compound is administered to the patient, or when thepatient undergoes a specific therapy. Typically the voice annotationuses the same speaker used for the two-way communication system. It alsomay include a speech-to-text converter that converts audio annotationsfrom the clinician into text fields that can be easily stored alongsidethe vital sign information. In embodiments, both a text field and theoriginal audio annotation are stored in a computer memory (e.g.database), and can be edited once stored. In other embodiments, apre-determined text field (indicating, e.g., that a specific medicationis delivered at a time/date automatically determined by the transceiver)is used to annotate the vital sign information. In still otherembodiments, a set of parameters determined from the digital audiosignals can include an icon or a numerical value. Annotations in thedatabase can be viewed afterwards using a GUI that renders both thevital sign information (shown, e.g., in a graphical form) and one ormore of the annotations (e.g. icon, text field, numerical value, orvoice annotation).

In another aspect, the invention provides a wrist-worn transceiverfeaturing a GUI that the patient can use to indicate their level ofpain. Here, the GUI typically includes a touchpanel display configuredto render a set of input fields, with each input field in the setindicating a different level of pain. Once contacted, the input fieldsgenerate a signal that is processed to determine the patient's level ofpain. This signal can be further processed and then wirelesslytransmitted to a remote computer for follow-on analysis.

In embodiments, the touchpanel display features a touch-sensitive areaassociated with each input field that generates a digital signal (e.g. anumber) after being contacted. Each input field is typically a uniquegraphical icon such as a cartoon or numerical value indicating anescalating level of pain. The transceiver can also include a voiceannotation system similar to that described above so the patient canspecifically describe their pain (e.g. its location) using their ownvoice. This information can be wirelessly transmitted to a remotecomputer (e.g. a PDS) featuring a display device (e.g. an RVD). Thissystem can render both vital sign information and a parameter determinedfrom the pain signal, and can additionally include an alarming systemthat activates an alarm if the pain signal or a parameter calculatedtherefrom exceeds a pre-determined threshold.

In a related aspect, the invention provides a wrist-worn transceiverthat includes a mentation sensor configured to collect data inputcharacterizing the patient's level of mentation (e.g. mental acuity).This information, along with traditional vital signs and the waveformsthey are calculated from, is wirelessly transmitted to a remote computerfor analysis. In embodiments, the mentation sensor is a touchpaneldisplay that renders a GUI to collect information characterizing thepatient's level of mentation. For example, the GUI can render a seriesof icons, a game, test, or any other graphical or numerical constructthat can be used to evaluate mentation. In a specific embodiment, forexample, the GUI includes a set of input fields associated with anumerical value. Here, the mentation ‘test’ features an algorithm todetermine if the input fields are contacted by the patient in apre-determined numerical order. Upon completion, the test results can beevaluated to generate a mentation ‘score’. In this aspect, thewrist-worn transceiver also includes a two-way communication system thatreceives audio information from the patient. This audio information canbe used for conventional communication purposes, and can additionally beanalyzed to further gauge mentation. As in previous embodiments, thementation score can be sent with vital sign information to a PDS/RVD forfollow-on analysis. These systems may include an alarming system thatgenerates an alarm if the mentation parameter or a parameter calculatedtherefrom exceeds a pre-determined threshold.

In another aspect, the invention provides a wrist-worn transceiverfeaturing a motion sensor (e.g. an accelerometer, mercury switch, ortilt switch) that generates a motion signal indicating the transceiver'sorientation. The processing component within the transceiver processesthe motion signal and, in response, orients the GUI so that it can beeasily viewed in ‘rightside up’ configuration, i.e. with text renderedin a conventional manner from left to right. If the transceiver is moved(e.g., so that it is viewed by a clinician instead of a patient), theaccelerometers generate new motion signals, and the GUI is ‘flipped’accordingly. Typically, for example, the GUI is rendered in either afirst orientation or a second orientation, with the two orientationsseparated by 180 degs., and in some cases by 90 degs. In embodiments,the first orientation corresponds to a ‘patient GUI’, and the secondorientation corresponds to a ‘clinician GUI’. This allows, for example,the appropriate GUI to be automatically rendered depending on thetransceiver's orientation. The clinician GUI typically includes medicalparameters, such as vital signs and waveforms, whereas the patient GUItypically includes non-medical features, such as a ‘nurse call button’,time/date, and other components described in more detail below.

In preferred embodiments, the motion sensor is a 3-axis accelerometerconfigured to generate a time-domain ACC waveform. During a measurement,the processing component additionally analyzes the waveform to determineparameters such as the patient's motion, posture, arm height, and degreeof motion.

In another aspect of the invention, the wrist-worn transceiver featuresa display device configured to render at least two GUIs, with the firstGUI featuring medical content, and the second GUI featuring non-medicalcontent relating to entertainment, food service, games, and photographs.The photograph, for example, can include an image of the patient or arelative of the patient; this latter case may be particularly useful inneo-natal hospital wards. To capture the photograph, the body-wornmonitor may include a digital camera, or a wireless interface to aremote digital camera, such as that included in a portable computer orcellular telephone.

In other embodiments, the second GUI is configured to render menusdescribing entertainment content, such as television (e.g. differentchannels or pre-recorded content), movies, music, books, and videogames. In this case, the touchpanel display can be used to select thecontent or, in embodiments, play a specific game. The wirelesstransmitter within the transceiver is further configured to transmit andreceive information from a remote server configured to store digitalrepresentations of these media sources. In still other embodiments, thesecond GUI is configured to display content relating to a food-servicemenu. Here, the wireless transmitter is further configured to transmitand receive information from a remote server configured to interfacewith a food-service system.

In another aspect, the invention provides a system for monitoring apatient that includes a vital sign monitor configured to be worn on thepatient's body, and a remote computer. The vital sign monitor featuresconnection means (e.g. a flexible strap or belt) configured to attach atransceiver to the patient's body, and sensor with a sensing portion(e.g. electrodes and an optical sensor) that attaches to the patient tomeasure vital sign information. A mechanical housing included in thetransceiver covers a wireless decoder, processing component, andwireless transmitter, and supports a display component. The wirelessdecoder (e.g. a barcode scanner or radio frequency identification (RFID)sensor) is configured to detect information describing a medication, amedication-delivery rate, a clinician, and the patient. For example,this information may be encoded in a barcode or RFID tag located on thepatient, clinician, medication, or associated with an infusion pump. Theprocessing component is configured to process: 1) the vital signinformation to generate a vital sign and a time-dependent waveform; and2) information received by the wireless decoder to generate decodedinformation. The wireless transmitter within the mechanical housingreceives information from the processing component, and transmits it toa remote computer. In response the remote computer processes theinformation and transmits an information-containing packet back to thevital sign monitor.

In embodiments, the remote computer performs an analyzing step thatcompares information describing both the medication and the patient todatabase information within a database. The database may include, forexample, a list of acceptable medications and acceptablemedication-delivery rates corresponding to the patient. In some casesboth the vital sign information and the decoded information arecollectively analyzed and compared to values in the database to affecttreatment of the patient. For example, this analysis may determine thata patient with a low blood pressure should not receive medications thatfurther lower their blood pressure. Or it may suggest changing a dosagelevel of the medication in order to compensate for a high heart ratevalue. In general, the remote computer can analyze one or more vitalsign values corresponding to a patient, along with the patient'sdemographic information, medical history, and medications, and determineacceptable medications and medication-delivery rates based on thisanalysis. In response, the computer can transmit a packet back to thevital sign monitor, which renders its contents on the display. Thepacket can include a message confirming that a particular medication andmedication-delivery rate are acceptable for the patient, and may alsoinclude a set of instructions for delivering the medication andperforming other therapies.

Still other embodiments are found in the following detailed descriptionof the invention, and in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic drawing showing the wrist-worn transceiver of theinvention attached to a patient's wrist;

FIGS. 2A and 2B show, respectively, schematic drawings of the wrist-worntransceiver of FIG. 1 oriented ‘rightside up’ so that a patient can viewthe GUI, and ‘upside down’ so that a clinician can view the GUI;

FIG. 3 shows a schematic drawing of the wrist-worn transceiver of FIG. 1and a list of features available in both a patient GUI and a clinicianGUI;

FIG. 4 shows a schematic drawing of the body-worn monitor featuringsensors for measuring ECG, PPG, ACC, OSC, and IP waveforms, and systemsfor processing these to determine a patient's vital signs;

FIG. 5 shows a schematic drawing of an IT configuration of the inventionwhere the body-worn monitor of FIG. 4 is connected through a wirelessnetwork to a PDS and hospital EMR;

FIGS. 6A and 6B show, respectively, schematic drawings of a newtransceiver having a fully charged battery being swapped with anoriginal transceiver having a depleted battery before and afterdeploying the ‘bump’ methodology;

FIG. 7 shows a schematic drawing of transceivers undergoing the ‘bump’methodology of FIGS. 6A and 6B and wirelessly transmitting their ACCwaveforms to the PDS for analysis;

FIG. 8 shows screen captures from a GUI used to guide a clinicianthrough the ‘bump’ methodology of FIGS. 6A, 6B, and 7;

FIG. 9 shows a schematic drawing of a transceiver being ‘bumped’ againsta RVD in order to pair the two devices;

FIG. 10 shows a map indicating how the transceiver and RVD of FIG. 9 arepaired to each other;

FIG. 11 shows a schematic drawing of the wrist-worn transceiver of FIG.1 being used for voice annotation of a patient's vital sign data;

FIG. 12 shows a schematic drawing of the wrist-worn transceiver of FIG.11 wirelessly transmitting voice annotations to the PDS for analysis;

FIG. 13 shows screen captures from a GUI used to guide a clinicianthrough the voice annotation methodology of FIGS. 11 and 12;

FIG. 14 shows screen captures from a GUI used when the wrist-worntransceiver functions as a two-way communicator between the patient anda clinician;

FIG. 15 shows a screen capture from a GUI used to render a ‘pain index’on the wrist-worn transceiver;

FIG. 16 shows a screen capture from a GUI used to render a mentationtest on the wrist-worn transceiver;

FIG. 17 shows a screen capture from a GUI used to render a photograph ofthe patient on the wrist-worn transceiver;

FIG. 18 shows a screen capture from a GUI used to render a food menu onthe wrist-worn transceiver;

FIG. 19 shows a screen capture from a GUI used to render a menu oftelevision channels on the wrist-worn transceiver;

FIG. 20 shows a schematic drawing of the barcode scanner in thewrist-worn transceiver scanning barcodes associated with a patient,clinician, and medication, and sending the decoded barcode informationto the PDS;

FIGS. 21A and 21B show three-dimensional images of the body-worn monitorof FIG. 4 attached to a patient with and without, respectively, acuff-based pneumatic system used for a calibrating indexing measurement;

FIGS. 22A and 22B show, respectively, three-dimensional images of thewrist-worn transceiver before and after receiving cables from othersensors within the body-worn monitor;

FIG. 23A shows a schematic drawing of a patient wearing the body-wornmonitor of FIG. 21B and its associated sensors;

FIG. 23B shows graphs of time-dependent ECG, PPG, OSC, ACC, and IPwaveforms generated with the body-worn monitor and sensors of FIG. 23A;

FIG. 24 shows screen captures from a GUI used to render vital signs andECG, PPG, and IP waveforms on the wrist-worn transceiver;

FIG. 25 shows a schematic drawing of the ACC, ECG, pneumatic, andauxiliary systems of the body-worn monitor communicating over the CANprotocol with the wrist-worn transceiver;

FIG. 26 shows an alternate IT configuration of the invention where thewrist-worn transceiver of FIG. 1 communicates with the PDS through awireless access point connected to the Internet;

FIG. 27 shows an alternate IT configuration of the invention where thewrist-worn transceiver of FIG. 1 communicates with the PDS through awireless device connected to the Internet; and

FIG. 28 shows an alternate IT configuration of the invention where thewrist-worn transceiver of FIG. 1 communicates with the PDS through aninternal cellular modem connected to the Internet.

DETAILED DESCRIPTION OF THE INVENTION

System Overview

FIG. 1 shows a transceiver 72 according to the invention that attachesto a patient's wrist 66 using a flexible strap 90. The transceiver 72connects through a first flexible cable 92 to a thumb-worn opticalsensor 94, and through a second flexible cable 82 to an ECG circuit anda series of chest-worn electrodes (not shown in the figure). During ameasurement, the optical sensor 94 and chest-worn electrodes measure,respectively, time-dependent optical waveforms (e.g. PPG) and electricalwaveforms (e.g. ECG and IP), which are processed as described below todetermine vital signs and other physiological parameters such as cNIBP,SpO2, HR, RR, TEMP, pulse rate (PR), and cardiac output (CO). Oncemeasured, the transceiver 72 wirelessly transmits these and otherinformation to a remote PDS and RVD. The transceiver 72 includes atouchpanel display that renders a GUI 50 which, in turn, displays thevital signs, physiological parameters, and a variety of other featuresdescribed in detail below. Collectively, the transceiver 72 and GUI 50incorporate many features that are normally reserved for non-medicalapplications into a body-worn vital sign monitor that continuouslymonitors ambulatory patients as they move throughout the hospital.

The transceiver 72 includes an embedded accelerometer that senses itsmotion and position, and in response can affect properties of the GUI.Referring to FIGS. 2A and 2B, for example, time-resolved ACC waveformsfrom the accelerometer can be processed with a microprocessor within thetransceiver to detect orientation of the touchpanel display. Thisinformation can then be analyzed to determine if it is the clinician orpatient who is viewing the display. In response, the GUI can ‘flip’ sothat it is properly oriented (i.e. ‘rightside up’, as opposed to beingupside down) for the viewer. For example, as shown in FIG. 2A, when thetransceiver 72 is worn on the patient's right wrist 66 the internalaccelerometer generates ACC waveforms that are processed by themicroprocessor to determine this orientation. The GUI 50A is adjustedaccording so that it is always oriented with numbers and text arrangedrightside up and read from left to right. When the patient's arm isrotated, as shown in FIG. 2B, the ACC waveforms change accordinglybecause the accelerometer's axes are swapped with respect to gravity.Such a situation would occur, for example, if a clinician were to orientthe patient's arm in order read the transceiver's display. In this case,the ACC waveforms are processed to determine the new orientation, andthe GUI 50B is flipped so it is again rightside up, and can be easilyread by the clinician.

The internal accelerometer can also detect if the transceiver is‘bumped’ by an external object. In this case, the ACC waveform willfeature a sharp ‘spike’ generated by rapid acceleration and decelerationcaused by the bumping process. As described in detail below, such abumping process can serve as a fiducial marker that initiates a specificevent related to the transceiver, such as a battery swap or process thatinvolves pairing the transceiver to an external wireless system ordisplay.

The accelerometer within the transceiver, when combined with otheraccelerometers within the body-worn monitor, can also be used todetermine the patient's posture, activity level, arm height and degreeof motion, as described in detail below. Use of one or moreaccelerometers to detect such motion-related activities is described,for example, in the following patent applications, the contents of whichare incorporated herein by reference: BODY-WORN MONITOR FEATURING ALARMSYSTEM THAT PROCESSES A PATIENT'S MOTION AND VITAL SIGNS (U.S. Ser. No.12/469,182; filed May 20, 2009) and BODY-WORN VITAL SIGN MONITOR WITHSYSTEM FOR DETECTING AND ANALYZING MOTION (U.S. Ser. No. 12/469,094;filed May 20, 2009).

Referring to FIG. 3, in addition to the GUI 50, the transceiver 72includes a high-fidelity speaker 120, a microphone 101, and a barcodescanner 102 which, respectively, enunciates audible information,measures voice signals from both the patient and a clinician, and scansgraphical barcodes to decode numerical information describing thepatient and their medication. Signals from these and other componentsare processed to supply information to either a ‘patient GUI’ 52 or a‘clinician GUI’ 54. The patient GUI 52, for example, typically includesfeatures that are decoupled from a standard clinical diagnosis; theseinclude a nurse call button, voice communications, a ‘pain’ index, amentation test to estimate the patient's cognitive abilities, mealordering within the hospital, games, and a controller for entertainmentcontent, e.g. to adjust parameters (e.g. channels, volume) for astandard television set. The clinical GUI 54, in comparison, includesfeatures that are used for clinical diagnoses and for operating thetransceiver in a hospital environment. The primary features of this GUI54 include displaying vital signs (e.g. cNIBP, SpO2, HR, RR, TEMP),other medical parameters (e.g. PR, CO), and waveforms (PPG, ECG, IP).Secondary features of the clinical GUI include voice communications,battery-change and pairing operations using the above-described ‘bump’methodology, voice annotation of medical records and diagnoses, a methodfor checking medications using the barcode scanner 102, and display of aphotograph or video describing the patient.

During normal operation, the GUI renders 50 simple icons indicating thatthe transceiver is powered on and operational (e.g., a ‘beating heart’),the strength of the wireless signal (e.g. a series of bars withescalating height), and the battery level (e.g. a cartoon of a batterywith a charge-dependent gauge). The transceiver 72 displays these iconsuntil the touchpanel display is contacted by either the patient or aclinician. This process yields the patient GUI 52, which features alarge icon 57 showing a telephone (which is used for nurse callapplications, as described below), and a smaller icon 53 showing a lockwhich, when tapped, enables the clinician to ‘unlock’ the transceiverand utilize the clinician interface 54. The transceiver 72 immediatelyrenders a GUI that shows vital signs and waveform information if thepatient's physiological condition requires immediate medical attention,e.g. in the case of cardiac arrest.

The clinician interface 54 is password-protected to prevent the patientor any other non-clinician from viewing important and potentiallyconfusing medical information. A password can either be entered as astandard personal identification number (PIN) by tapping keys on anumerical keypad (as shown in FIG. 3), or by simply swiping a barcodeprinted on the clinician's hospital badge across the barcode scanner102. The microprocessor within the transceiver unlocks the clinicianinterface following either of these events, and enables all the featuresassociated with the interface, which are described in detail below. Forexample, with this interface the clinician can view vital signs andwaveforms to make a medical diagnosis, as described with reference toFIG. 24. If the transceiver's battery charge is running low, theclinician can swap in a new transceiver and transfer data from theoriginal transceiver simply by ‘bumping’ the two transceivers together,as described with reference to FIGS. 6-8. Medical records can bevoice-annotated and stored on the PDS or a hospital's EMR using theprocess shown in FIGS. 11-13. The patient's medication can be checked byscanning and processing information encoded in barcodes associated withthe patient, clinician, and medication, as shown in FIG. 20. All of thisfunctionality is programmed within the transceiver and the body-wornmonitor, and can be accomplished without tethering the patient to aconventional vital sign monitor typically mounted on a wall in thehospital or a rolling stand. Ultimately this allows the patient to weara single body-worn monitor as they transition throughout the variousfacilities within the hospital, e.g. the ED, ICU, x-ray facility, andoperating room.

Hardware in Body-Worn Monitor

FIGS. 4 and 5 show schematic drawings of a body-worn monitor 100 used tomeasure vital signs from a patient and render the different GUIsdescribed above (FIG. 4), along with a wireless system over which thetransceiver 72 sends information through a hospital network 60 to eithera remote RVD, e.g. a computer 62 or hand-held device 64 (FIG. 5).Referring to FIG. 4, the body-worn monitor 100 features a wrist-worntransceiver 72 that continuously determines vital signs andmotion-related properties from an ambulatory patient in a hospital. Themonitor 100 is small, lightweight, and comfortably worn on the patient'sbody during their stay in the hospital; its specific form factor isdescribed in detail below with reference to FIGS. 21 and 22. It providescontinuous monitoring, and features a software framework that determinesalarms/alerts if the patient begins to decompensate. Such systems aredescribed in the following co-pending patent applications, the contentsof which have been previously incorporated herein by reference:BODY-WORN MONITOR FEATURING ALARM SYSTEM THAT PROCESSES A PATIENT'SMOTION AND VITAL SIGNS (U.S. Ser. No. 12/469,182; filed May 20, 2009)and BODY-WORN VITAL SIGN MONITOR WITH SYSTEM FOR DETECTING AND ANALYZINGMOTION (U.S. Ser. No. 12/469,094; filed May 20, 2009). The frameworkprocesses both the patient's motion and their vital sign informationwith algorithms that reduce the occurrence of false alarms.

A combination of features makes the body-worn monitor 100 ideal forambulatory patients within the hospital. For example, as shown in FIG.5, the transceiver 72 features a wireless transmitter 224 thatcommunicates through a collection of wireless access points 56 (e.g.routers based on 802.11 protocols) within a hospital network 60, whichincludes a PDS. From the PDS 60 data are sent to an RVD (e.g. a portabletablet computer 62) located at a central nursing station, or to a localcomputer (e.g. a hand-held PDA 64) carried by the clinician. Inembodiments, data can be sent to the PDA 64 through a peer-to-peerwireless connection. The specific mode of communication can bedetermined automatically (using, e.g., a signal strength associated withthe wireless connection), or manually through an icon on the GUI.

The transceiver 72 features a CPU 222 that communicates through adigital CAN interface, or bus, to external systems featuring ECG 216,external accelerometers 215 b-c, pneumatic 220, and auxiliary 245sensors. Each sensor 215 b-c, 216, 220, 245 is ‘distributed’ on thepatient to minimize the bulk and weight normally associated withconventional vital sign monitors, which typically incorporate allelectronics associated with measuring vital signs in a single plasticbox. Moreover, each of these sensors 215 b-c, 216,220, 245 generatedigital signals close to where they actually attach to the patient, asopposed to generating an analog signal and sending it through arelatively long cable to a central unit for processing. This can reducenoise due to cable motion which is often mapped onto analog signals.Cables 240, 238, 246 used in the body-worn monitor 210 to transmitpackets over the CAN bus typically include five separate wires bundledtogether with a single protective cladding: the wires supply power andground to the remote ECG system 216, accelerometers 215 b-c, pneumatic220, and auxiliary systems 245; provide high/low signal transmissionlines for data transmitted over the CAN protocol; and provide a groundedelectrical shield for each of these four wires. There are severaladvantages to this approach. First, a single pair of transmission linesin the cable (i.e. the high/low signal transmission lines) can transmitmultiple digital waveforms generated by completely different sensors.This includes multiple ECG waveforms (corresponding, e.g., to vectorsassociated with three, five, and twelve-lead ECG systems) from the ECGcircuit, along with ACC waveforms associated with the x, y, and z axesof accelerometers within the body-worn monitor 100. The same two wires,for example, can transmit up to twelve ECG waveforms (measured by atwelve-lead ECG system), and six ACC waveforms (measured by theaccelerometers 215 b-c). Limiting the transmission line to a pair ofconductors reduces the number of wires attached to the patient, therebydecreasing the weight and any cable-related clutter. Second, cablemotion induced by an ambulatory patient can change the electricalproperties (e.g. electrical impendence) of its internal wires. This, inturn, can add noise to an analog signal and ultimately the vital signcalculated from it. A digital signal, in contrast, is relatively immuneto such motion-induced artifacts.

The ECG 216, pneumatic 220, and auxiliary 245 systems are stand-alonesystems that each includes a separate CPU, analog-to-digital converter,and CAN transceiver. During a measurement, they connect to thetransceiver 72 through cables 240, 238, 246 and connectors 230, 228, 232to supply digital inputs over the CAN bus. The ECG system 216, forexample, is completely embedded in a terminal portion of its associatedcable. Systems for three, five, and twelve-lead ECG monitoring can beswapped in an out simply by plugging the appropriate cable (whichincludes the ECG system 216) into a CAN connector 230 on the wrist-worntransceiver 72, and the attaching associated electrodes to the patient'sbody.

As described above, the transceiver 72 renders separate GUIs that can beselected for either the patient or a clinician. To do this, it includesa barcode scanner 242 that can scan a barcode printed, e.g., on theclinician's badge. In response it renders a GUI featuring information(e.g. vital signs, waveforms) tailored for a clinician that may not besuitable to the patient. So that the patient can communicate with theclinician, the transceiver 72 includes a speaker 241 and microphone 237interfaced to the CPU 222 and wireless system 224. These componentsallow the patient to communicate with a remote clinician using astandard VOIP protocol. A rechargeable Li:ion battery 239 powers thetransceiver 72 for about four days on a single charge. When the batterycharge runs low, the entire transceiver 72 is replaced using the ‘bump’technique described in detail below.

Three separate digital accelerometers 215 a-c are non-obtrusivelyintegrated into the monitor's form factor; two of them 215 b-c arelocated on the patient's body, separate from the wrist-worn transceiver72, and send digitized, motion-related information through the CAN busto the CPU 222. The first accelerometer 215 a is mounted on a circuitboard within the transceiver 72, and monitors motion of the patient'swrist. The second accelerometer 215 b is incorporated directly into thecable 240 connecting the ECG system 216 to the transceiver 72 so that itcan easily attach to the patient's bicep and measure motion and positionof the patient's upper arm. As described below, this can be used toorient the screen for viewing by either the patient or clinician.Additionally, signals from the accelerometers can be processed tocompensate for hydrostatic forces associated with changes in thepatient's arm height that affect the monitor's cNIBP measurement, andcan be additionally used to calibrate the monitor's blood pressuremeasurement through the patient's ‘natural’ motion. The thirdaccelerometer 215 c is typically mounted to a circuit board thatsupports the ECG system 216 on the terminal end of the cable, andtypically attaches to the patient's chest. Motion and position of thepatient's chest can be used to determine their posture and activitystates, which as described below can be used with vital signs forgenerating alarm/alerts. Each accelerometer 215 a-c measures threeunique ACC waveforms, each corresponding to a separate axis (x, y, or z)representing a different component of the patient's motion. To determineposture, arm height, activity level, and degree of motion, thetransceiver's CPU 222 processes signals from each accelerometer 215 a-cwith a series of algorithms, described in the following pending patentapplications, the contents of which have been previously incorporatedherein by reference: BODY-WORN MONITOR FEATURING ALARM SYSTEM THATPROCESSES A PATIENT'S MOTION AND VITAL SIGNS (U.S. Ser. No. 12/469,182;filed May 20, 2009) and BODY-WORN VITAL SIGN MONITOR WITH SYSTEM FORDETECTING AND ANALYZING MOTION (U.S. Ser. No. 12/469,094; filed May 20,2009). In total, the CPU 222 can process nine unique, time-dependentsignals corresponding to the three axes measured by the three separateaccelerometers. Algorithms determine parameters such as the patient'sposture (e.g., sitting, standing, walking, resting, convulsing,falling), the degree of motion, the specific orientation of thepatient's arm and how this affects vital signs (particularly cNIBP), andwhether or not time-dependent signals measured by the ECG 216, optical218, or pneumatic 220 systems are corrupted by motion.

To determine blood pressure, the transceiver 72 processes ECG and PPGwaveforms using a measurement called with Composite Technique, which isdescribed in the following patent application, the contents of whichhave been previously incorporated herein by reference: BODY-WORN SYSTEMFOR MEASURING CONTINUOUS NON-INVASIVE BLOOD PRESSURE (cNIBP) (U.S. Ser.No. 12/650,354; filed Nov. 15, 2009). The Composite Technique measuresECG and PPG waveforms with, respectively, the ECG 216 and optical 218systems. The optical system 218 features a thumb-worn sensor thatincludes LEDs operating in the red (λ˜660 nm) and infrared (λ˜900 nm)spectral regions, and a photodetector that detects their radiation afterit passes through arteries within the patient's thumb. The ECG waveform,as described above, is digitized and sent over the CAN interface to thewrist-worn transceiver 72, while the PPG waveform is transmitted in ananalog form and digitized by an analog-to-digital converter within thetransceiver's circuit board. The pneumatic system 220 provides adigitized pressure waveform and oscillometric blood pressuremeasurements through the CAN interface; these are processed by the CPU222 to make cuff-based ‘indexing’ blood pressure measurements accordingto the Composite Technique. The indexing measurement typically onlytakes about 40-60 seconds, after which the pneumatic system 220 isunplugged from its connector 228 so that the patient can move within thehospital without wearing an uncomfortable cuff-based system. The opticalwaveforms measured with the red and infrared wavelengths canadditionally be processed to determine SpO2 values, as described indetail in the following patent application, the contents of which isincorporated herein by reference: BODY-WORN PULSE OXIMETER (U.S. Ser.No. 12/559,379; filed Sep. 14, 2009).

Collectively, these systems 215 a-c, 216, 218, and 220 continuouslymeasure the patient's vital signs and motion, and supply information tothe software framework that calculates alarms/alerts. A third connector232 also supports the CAN bus and is used for auxiliary medical devices245 (e.g. a glucometer, infusion pump, system for measuring end-tidalCO2) that is either worn by the patient or present in their hospitalroom.

Once a measurement is complete, the transceiver 72 uses the internalwireless transmitter 224 to send information in a series of packets to aPDS 60 within the hospital. The wireless transmitter 224 typicallyoperates on a protocol based on 802.11, and can communicate with the PDS60 through an existing network within the hospital as described abovewith reference to FIG. 5. Information transmitted by the transceiveralerts the clinician if the patient begins to decompensate. The PDS 60typically generates this alarm/alert once it receives the patient'svital signs, motion parameters, ECG, PPG, and ACC waveforms, andinformation describing their posture, and compares these parameters topreprogrammed threshold values. As described in detail below, thisinformation, particularly vital signs and motion parameters, is closelycoupled together. Alarm conditions corresponding to mobile andstationary patients are typically different, as motion can corrupt theaccuracy of vital signs (e.g., by adding noise), and induce artificialchanges in them (e.g., through acceleration of the patient's heart andrespiratory rates) that may not be representative of the patient'sactual physiology.

Swapping and Pairing Transceivers Using ‘Bump’ Methodology

FIGS. 6A, 6B, 7, and 8 show how a wrist-worn transceiver 72A with adepleted battery can be swapped with a similar transceiver 72B having afully charged battery using the ‘bump’ methodology described above.Prior to the swap, as shown in FIG. 6A, both transceivers are readied byactivating the appropriate GUI 50C, 50D following the screens shown inFIG. 8. This process activates firmware on each transceiver 72A, 72Bindicating that the swap is about to occur. In response, eachtransceiver sends a packet through the wireless access point 56 and tothe hospital network and PDS 60. The packet describes atransceiver-specific address, e.g. a MAC address associated with itswireless transmitter. Once this is done, the GUIs 50C, 50D on bothtransceivers 72A, 72B indicate to a clinician that they can be ‘bumped’together, and that the swap can proceed.

At this point, as shown in FIG. 6A, the new transceiver 72B (with thefully charged battery) is then bumped against the old transceiver 72A(with the depleted battery). Internal accelerometers within bothtransceivers 72A, B detect the bumping process and, in response,independently generate ACC waveforms 130, 132, both featuring a sharpspike indicating the rapid acceleration and deceleration due to thebumping process. Typically the ACC waveforms 130, 132 correspond to thesame axes in both transceivers. The ACC waveforms are digitized withineach transceiver and then transmitted through the wireless access point56 to the PDS 60, where they are stored in a computer memory andanalyzed with a software program that is activated when both devices are‘readied’, as described above. The software program compares formattedversions of the ACC waveforms 130′, 132′ to detect the rapid spikes, asshown by the graph 140 in FIG. 7. The rapid spikes in the waveforms130′, 132′ should occur within a few microseconds of each other, asindicated by the shaded window 142 in the graph 140. Other transceiversoperating on the network may generate similar motion-related spikes dueto movements of the patient wearing them, but the probability that suchspikes occur at the exact same time as the transceivers being swapped isextremely low. The software program interprets the concurrence of thespikes as indicating that data stored on the old transceiver 72A is tobe transferred to the new transceiver 72B. The data, for example,includes demographic information describing the patient (e.g. theirname, age, height, weight, photograph), the medications they are taking,and all the vital sign and waveform information stored in memory in theold transceiver 72A. Following the bump, this information is associatedwith the address corresponding to the new transceiver 72B. At this timeinformation may also be sent from the PDS so it can be stored locally onthe new transceiver. When all the relevant information is transferredover, the GUIs 50C, 50D on both transceivers 72A, 72B indicate that theycan be swapped. At this point, cables connected to the optical sensorand ECG electrodes are unplugged from the old transceiver 72A, andplugged into the new transceiver 72B. The clinician then attaches thenew transceiver to the patient's wrist, and commences measuring vitalsigns from the patient as described above.

In other embodiments, a time period corresponding to a portion (e.g. apeak value) of the motion-generated spike is determined on each of thewrist-worn transceivers that are bumped together. Each transceiver thensends its time period to the PDS, where they are collectively analyzedto determine if they are sufficiently close in value (e.g. within a fewhundred milliseconds). If this criterion is met, software on the PDSassumes that the transceivers are ready to be swapped, and performs theabove-described steps to complete this process.

FIG. 8 shows a sequence of screens within the GUI that describe theprocess for swapping transceivers to the clinician. The process beginswhen a screen 158 rendered by Device A indicates that its battery isrunning low of charge. This is indicated by a standard ‘low battery’icon located in the upper right-hand corner of the screen 158, as wellas a larger icon located near the bottom of the screen. A timedescribing the remaining life of the battery appears near this icon whenthis time is 5 minutes or less. Each transceiver includes a sealedinternal Li:ion battery that cannot be easily replaced in the hospital.Instead, the transceiver is inserted in a battery charger that typicallyincludes eight or sixteen ports, each of which charges a separatetransceiver. To swap Device A with Device B, the clinician taps thescreen 158 to yield a new screen 160 which includes a series of sixicons, each related to a unique feature. The icon in the lower left-handcorner shows two interchanging batteries. When tapped, this icon yieldsa new screen 160 indicating that Device A is ready to be swapped. DeviceB is then removed from a port in the battery charger, and a sequence ofscreens 150, 152, 154 are initiated as described with reference toDevice A.

When Devices A and B both show, respectively, screens 162, 154, they areready to be swapped using the ‘bumping’ process. At this point, asdescribed above, a clinician ‘bumps’ Device B into Device A, which inturn generates two ACC waveforms 130, 132 featuring sharp,time-dependent spikes indicating the bump. The waveforms 130, 132include spikes, as shown by the shaded box 142, which are concurrent intime, and are wirelessly transmitted in a packet that indicates theirorigin through the pathway shown in FIG. 7 to the PDS. There, they areanalyzed by the software program described above to determine that dataassociated with Device A (e.g. patient information, vital signs) is nowassociated with Device B. When this association is complete, the PDStransmits a packet back through the pathway shown in FIG. 7 to bothDevice A and B, indicating that the PDS is ready to transfer the data.Device B then renders a screen 166 asking the clinician to confirm theprocess. Data is transferred if the clinician taps the ‘check’ box inthe lower right-hand corner of the screen; during this process Device Brenders a screen 168 that shows the patient's name to further confirmwith the clinician that the transfer process is valid. When it iscomplete, Device A is no longer active, meaning it cannot collect dataor generate alarms. Device B renders a screen 170 that instructs theclinician to disconnect the optical and electrical sensors from DeviceA, and to clean this device and insert it into the battery charger.During this process all alarms are paused for Device B. A screen 172 onDevice B then instructs the clinician to connect the sensors and attachDevice B to the patient's wrist. When this is complete, Device B rendersa final confirmatory screen 176, which when checked finalizes theswapping process. At this point Device B is officially associated withthe patient, renders a standard screen 178, and commences measuringvital signs from the patient. These vital signs, along with thosecollected from Device A, are included in a contiguous data filecharacterizing the patient.

As an alternative to the ‘bumping’ process, Device B's barcode can beread and processed to facilitate swapping the transceivers. In thiscase, an icon on Device A, when tapped, renders a screen 164 indicatingthat Device A is ready to read the barcode printed on Device B. At thispoint, Device B's barcode is swiped across Device A's barcode reader,decoded, and wirelessly transmitted to the PDS as indicated in FIG. 7.The PDS uses this information to associate Device B with the patient asdescribed above. Once this is complete, Device B uses the same screensused for the ‘bumping’ transfer process (screens 166, 168, 170, 172,176, 178) to associate Device B with the patient. The ‘bumping’ processshown in FIG. 6 takes place along the long axes of Device A and DeviceB. Alternatively, it can take place along the short axes of thesedevices. Or the short axis of one device can be bumped against the longaxis of the other device to initiate the process.

The ‘bumping’ process described above can also be used for otherapplications relating to the wrist-worn transceiver. It can be used, forexample, to pair the transceiver with an RVD, such as a display locatedat the patient's bedside, or at a central nursing station. In thisembodiment, indicated in FIGS. 9 and 10, a clinician selects atransceiver 72 from the battery charger and brings it near an RVD 62.Before attaching the transceiver 72 to the patient, the clinician‘bumps’ it against a hard surface proximal to the RVD 62 (or against theRVD itself) to generate a sharp spike in the ACC waveform 133. Thewaveform 133 is similar in shape to that generated when two transceiversare swapped with the bumping process, as described above. The RVD'slocation needs to be determined in order to pair it with the transceiver72. To do this, at a pre-determined time period (e.g. every few minutes)all neighboring wireless access points 56A, 56B, 56C transmit a‘location beacon’ 59A, 59B, 59C to the transceiver, which is receivedand used to calculate a value for signal strength (typicallycharacterized by an ‘RSSI value’) between the transceiver 72 and therespective access point 56A, 56B, 56C. The transceiver concatenatesvalues for RSSI and identifiers for the access points into a single‘location packet’ 59D, which it then transmits along with the ACCwaveform 133 and an identifying code describing the transceiver (notshown in the figure) through a single access point 56B to the PDS 60.The PDS 60 receives the location packet 56D and parses it to arrive atRSSI values for the three wireless access points 56A, 56B, 56C withinwireless range of the transceiver 72. In other embodiments, theindividual access points 56A, 56B, 56C determine RSSI valuescharacterizing the signal strength between them and the transceiver, andsend these as individual packets to the PDS. Software on the PDS thenconcatenates these packets to determine signals similar to thoseincluded in the location packet.

Referring to FIG. 10, location-determining software operating on the PDStriangulates the signals, along with known locations of each wirelessaccess point 56A, 56B, 56C, to determine an approximate location 71 ofthe transceiver 72. The known locations of the access points are storedwithin a map grid 73 in a computer memory associated with thelocation-determining software. The transceiver's approximate locationtypically has an accuracy of 1-3 m. Using the map grid 73, the softwarethen processes the approximate location 71 and a known location of anyRVD 62 lying within a pre-determined radius 75. Typically thepre-determined radius is 3-5 m. If the location of the RVD 62 lieswithin the pre-determined radius 75, the RVD 62 is automatically‘paired’ with the transceiver 72. Once paired, the RVD 62 then displaysany follow-on waveform, motion, and vital sign information sent by thetransceiver.

In related embodiments, the location-determining software describedabove uses triangulation algorithms to determine the patient's currentand historical location. Such a process can be used to monitor andlocate a patient in distress, and is described, for example, in thefollowing issued patent, the contents of which are incorporated hereinby reference: WIRELESS, INTERNET-BASED, MEDICAL DIAGNOSTIC SYSTEM (U.S.Pat. No. 7,396,330). If triangulation is not possible, thelocation-determining software may simply use proximity to a wirelessaccess point (as determined from the strength of an RSSI value) toestimate the patient's location. Such a situation would occur if signalsfrom at least three wireless access points were not available. In thiscase, the location of the patient is estimated with an accuracy of about5-10 m. In embodiments, the RVD may be a central nursing station thatdisplays vital sign, motion-related properties (e.g. posture andactivity level) and location information from a group of patients. Suchembodiments are described in the following co-pending patentapplication, the contents of which are fully incorporated herein byreference: BODY-WORN VITAL SIGN MONITOR (U.S. Ser. No. 12/560,077, filedSep. 15, 2009). In other embodiments, the location-determining softwaredetermines the location of a patient-worn transceiver, and automaticallypairs it to a RVD located nearby (e.g. within a pre-determined radius,such as that shown in FIG. 10). In this way, the patient's informationcan be displayed on different RVDs as they roam throughout the hospital.

In embodiments, the patient's location can be analyzed relative to a setof pre-determined boundaries (e.g. a ‘geofence’) to determine if theyhave wandered into a restricted area. Or their speed can be determinedfrom their time-dependent location, and then analyzed relative to apre-determined parameter to determine if they are walking too fast. Ingeneral, any combination of location, motion-related properties, vitalsigns, and waveforms can be collectively analyzed with softwareoperating on either the transceiver or PDS to monitor the patient.Patients can be monitored, for example, in a hospital, medical clinic,outpatient facility, or the patient's home.

In the embodiments described above, location of the transceiver can bedetermined using off-the-shelf software packages that operate on thePDS. Companies that provide such software include, for example, by CiscoSystems (170 West Tasman Drive, San Jose, Calif. 93134; www.cisco.com),Ekahau (12930 Saratoga Avenue, Suite B-8, Saratoga, Calif. 95070;www.ekahau.com), and others.

In still other embodiments, software operating on the transceiver putsit into a ‘sleep mode’ when it is not attached to the patient. This waythe transceiver can determine and transmit a location packet even whenit is not used for patient monitoring. Using the above-describedlocation-determining software, this allows the transceiver's location tobe determined and then analyzed if it has been lost, misplaced, orstolen. For example, the transceiver's serial number can be entered intothe software and then used to send a ‘ping’ the transceiver. Thetransceiver responds to the ping by collecting and transmitting alocation packet as described above. Or the location of all unusedtransceivers can be automatically rendered on a separate interface. Instill other embodiments, the location-determining software can transmita packet to a specific transceiver (e.g. one that is stolen) to disableit from operating further.

In other embodiments, the ‘bumping’ process described above can be usedfor a variety of applications involving the body-worn monitor,wrist-worn transceiver, PDS, and RVD. In embodiments, for example, oneor more ‘bumps’ of a transceiver can modulate the ACC waveform, which isthen processed and analyzed to initiate a specific application.Applications include turning the transceiver on/off; attaching sensorsto the transceiver; pairing the transceiver with a hand-held device(e.g. a cellular phone or personal digital assistant) over apeer-to-peer connection (using, e.g., 802.11 or 802.15.4); pairing thetransceiver with a printer connected to a hospital network to print datastored in its computer memory; associating the transceiver with aspecific clinician; and initiating display of a particular GUI. Ingeneral, the ‘bumping’ process can be used to initiate any applicationthat can also be initiated with icons on the GUI.

Annotating the Medical Record Using the Wrist-Worn Transceiver

FIGS. 11-13 show how the wrist-worn transceiver can be used tocommunicate audible information from both the patient and a clinician.Audible information from the clinician 140 can be used, for example, toannotate vital sign information collected with the body-worn monitor.Audible information from the patient 141 can be transmitted to aclinician (e.g. a nurse working at a central station) to alert theclinician of a problem. In both applications, the transceiver 72 isattached to the patient's wrist 66 as described above and used tomeasure vital signs and waveform information. Audible information isreceived by a microphone 101 mounted on a circuit board within thetransceiver. A speaker 120 mounted to the same circuit board enunciatesvoice information to the patient. In these and other voice-relatedapplications, voice information is digitized by an internalanalog-to-digital converter within the transceiver, and then wirelesslytransmitted through a hospital's wireless network using conventionalVOIP protocols. Systems that operate these protocols are marketed, forexample, by Cisco Systems (170 West Tasman Drive, San Jose, Calif.93134; www.cisco.com), Skype (22/24 Boulevard Royal, 6e etage, L-2449,Luxembourg; www.skype.com), and others.

FIG. 12 describes the annotation process in more detail. In this case,the transceiver 72 within the body-worn monitor is attached to thepatient's wrist 66 to measure the patient's vital signs (e.g. bloodpressure). During the measurement process, the clinician uses the GUI50F to activate an ‘annotation’ function which enables the transceiverto receive audible signals 140 which are used, for example, to annotatedifferent medications administered to the patient. After the annotationfunction is activated, the clinician orally describes the medications.The microphone 101 within the transceiver 72 detects the voice signals,digitizes them with associated hardware, and then sends them and anassociated time/date sample using a VOIP protocol through an accesspoint 56 and to a PDS located within the hospital network 60. Vitalsigns are transmitted before and after the annotation function isactivated, and are stored along with the annotation in a computer memoryassociated with the PDS. Typically these data are stored within ahospital's EMR.

As shown in graph 141, annotated vital sign data can be viewedafterwards to determine, for example, how a patient responds to specificmedications. In this case, administration of a beta blocker as a meansof lowering the patient's blood pressure is recorded on the graph by awritten description of the annotation, along with an icon (a blacktriangle) indicating when it occurred in time. To generate the writtendescription the PDS requires software that performs a speech-to-textconversion. Such software is available, for example, from Nuance Systems(1 Wayside Road, Burlington, Mass. 01803; www.nuance.com). Similarly,the graph 141 shows a second annotation indicating that the patient washydrated with saline to increase their blood pressure.

FIG. 13 shows a series of screens within the GUI 50F that are used tocontrol the annotation process. As described above, to annotate medicalinformation the clinician taps an icon located in the upper right-handportion of screen 180. This action readies the voice recording featureswithin the transceiver. Tapping the annotation icon drives thetransceiver to render a second screen 182 that includes the type ofannotation, e.g. audible content relating to medication, a specificintervention or procedure, a medical assessment, or another subject.Typically annotations are delivered as audible speech, in which case the‘Speech’ button is tapped, as shown in screen 184. Alternatively theannotation can be text or numerical; these can be typed in, e.g., usinga ‘soft’ keyboard on the transceiver, or scanned in using thetransceiver's barcode scanner. The annotations can also be associatedwith an alarm condition, such as those shown on screens 181, 183, 185,187, 189, 191. Prior to recording an annotation, the GUI renders ascreen 188 that, once tapped, initiates the recording. The recording canalso be paused using screen 186. After it is complete, the cliniciantaps the ‘checkbox’ on the screen 188, thus saving the recording. It isthen sent to the PDS as shown in FIG. 12, and used to annotate thepatient's medical information.

Other forms of annotation are also possible with the transceiver. Forexample, it can include a small CCD camera that allows images of thepatient or their body (e.g. a wound) to be captured and used to annotatethe medical information. In other applications, a barcode printed onmedication administered to the patient can be scanned by thetransceiver's barcode scanner, and the information encoded therein canbe used to annotate vital sign information. In other embodiments, thetransceiver can integrate with other equipment in the hospital room(e.g. an infusion pump, ventilator, or patient-controlled anesthesiapump) through a wired or wireless connection, and information from thisequipment can be collected and transmitted to the PDS in order toannotate the vital sign information. In other embodiments, textannotations can be stored on the PDS, and then edited afterwards by theclinician.

Other GUI Applications

As shown in FIGS. 11 and 14, the speaker 120 and microphone 101 withinthe transceiver 72, combined with VOIP software operating on thehospital network, can also function as a nurse call system thatcommunicates both distress signals and voice information. Here, thetransceiver enables two-way communication between the patient and aremote clinician. During this application, the transceiver typicallyoperates the ‘patient GUI’, shown schematically in FIG. 3 and in moredetail in FIG. 14. Here, the GUI shows a single screen 192 thatindicates a nurse call function with an icon showing a telephone. Whenthe patient taps on the telephone the transceiver initiates a call to apre-programmed IP address, corresponding, e.g., to a computer at acentral nursing station or a VOIP-enabled phone. Alternatively thetransceiver can call a pre-programmed phone number corresponding to atelephone. While the call is being place the GUI renders a screen 194that shows the telephone's receiver being off the hook. A third screen196 indicates that the patient is connected to the clinician. The callis terminated when the patient finishes talking to the clinician andtaps the screen. Alternatively, the transceiver can include softwarethat detects that no further voice communications are taking place, andthen uses this information to terminate the call. In embodiments, theentire call can be stored in a computer memory on either the transceiveror the PDS.

The GUI operating on the wrist-worn transceiver's touchpanel display canrender several other interfaces that facilitate patient monitoring inthe hospital. For example, referring to FIG. 15, the GUI can be used tomonitor the patient's pain level, a parameter often considered byclinicians to be as important as vital signs for characterizing apatient. The GUI 200 shown in the figure features a simple series oficons that provide a relative indication of the patient's pain level. Anindex value of 0 (corresponding to a ‘happy’ face) indicates a low levelof pain; an index value of 10 (corresponding to a ‘sad’ face) indicatesa high level of pain. During a measurement, the patient simply touchesthe icon that best characterizes their pain level. The numerical valuecorresponding to this level is then wirelessly transmitted back to thePDS and stored in the patient's EMR. The GUI, for example, may beautomatically rendered periodically (e.g. every hour) on the transceiverto continuously monitor the patient's pain level. In other embodiments,the GUI could render a graphical display that provides a moresophisticated metric for determining the patient's pain, such as theMcGill Pain Questionnaire. This system described in the followingjournal article, the contents of which are incorporated herein byreference: ‘The McGill Pain Questionnaire: Major Properties and ScoringMethods’, Melzak, Pain, 1:277-299 (1975).

In a similar manner, the GUI can be used to gauge the patient's level ofmentation, i.e. mental activity. Mentation has been consistently shownto be a valuable tool for diagnosing a patient, but is typicallydetermined empirically by a clinician during a check-up or hospitalvisit. Such a diagnosis is somewhat arbitrary and requires the clinicianto meet face-to-face with the patient, which is often impractical. Butwith the wrist-worn transceiver, diagnosis of mentation can be madeautomatically at the patient's bedside without a clinician needing to bepresent. FIG. 16, for example, shows a GUI 202 that provides a simple‘mentation test’ for the patient to complete. In this case, thementation test involves a graphical representation of a series ofnon-sequential numbers. The patient completes this test by tapping onthe numbers rendered by the touchpanel display in their numerical order.An algorithm then ‘scores’ the test based on accuracy and the timerequired to complete it. Once determined, the score is wirelesslytransmitted back to the PDS, and then stored in the patient's EMR. Othersimple tests with varying complexity can be used in place of that shownin FIG. 16. The tests can vary depending on the specific mentationfunction to be tested. For example, unique tests can be generated forpatients with head injuries, cardiac patients, patients in severe pain,Alzheimer's patients, etc. In all cases, the tests are designed to makea quantitative assessment of the patient's mental status; thetransceiver sends a numerical value representing this parameter and anidentifier for the test back to the EMR for analysis. The transceivercan be programmed so that the GUI 202 for the mentation test, like theGUI 200 for pain level shown in FIG. 15, is automatically rendered atbasically any time interval on the touchpanel display. This timeinterval can be periodic and on an hourly basis, once/day, etc.

As shown in FIG. 17, the transceiver can include a GUI 204 that displaysa photograph or video of the patient. The photograph could be taken by adigital camera within the transceiver, or with an external camera andthen transferred to the transceiver through a variety of means, e.g. thehospital's wireless network, a peer-to-peer wireless connection, using anon-volatile memory such as an SD card, or even using a data-transferprocess initiated by the ‘bump’ methodology described above. In general,the same means used to port a photograph from a standard digital camerato a personal computer or other device can be used in this application.Once the photograph is received, software on the transceiver displays itin either a default screen (e.g., in place of the ‘beating heart’ shownin FIGS. 1 and 3), or when the GUI 204 is activated through a tap of acorresponding icon. Displaying the patient's photograph in this mannerprovides a visual indicator which the clinician can use to correctlyidentify the patient. In other embodiments, a photograph of someoneassociated with the patient (e.g. a relative) can also be displayed onthe GUI 204. Such an embodiment may be particularly useful for neo-natalhospitals wards, wherein one or more photographs of an infant's parentscould be displayed on a transceiver attached to the infant. This way aclinician could check the photograph to ensure that visitors to theneo-natal hospital ward are, in fact, the infant's parents.

FIGS. 18 and 19 show other GUIs 206, 208 that can be rendered on thewrist-worn transceiver's display to carry out basic features in thehospital, such as meal ordering (FIG. 18), and changing the channel on atelevision or computer (FIG. 19). In these cases, the PDS associatedwith the transceiver receives a packet describing the function at hand(e.g., the meal that has been ordered, or the channel that is desired),and communicates with another software application in the hospital tocomplete the transaction. This communication, for example, can takeplace using a XML-based Web Services operation, such as that describedin the following patent application, the contents of which areincorporated herein by reference: CUFFLESS BLOOD PRESSURE MONITOR ANDACCOMPANYING WEB SERVICES INTERFACE (U.S. Ser. No. 10/810,237, FiledMar. 26, 2004). In related embodiments, a GUI similar to that shown inFIG. 19 can be used to order movies, video games, television programsstored on a digital video recorder, books, and music. Contentcorresponding to these components is typically stored on a remoteserver, and then accessed using an XML-based operation, as describedabove.

In yet another application, as shown in FIG. 20, the wrist-worntransceiver 72 and its associated barcode scanner 102 can be used tocheck medication before it is administered to the patient. In thisembodiment, barcodes associated with the patient 63, clinician 65, andthe medication 67 are read by the barcode scanner 102 within thetransceiver 72. The transceiver then wirelessly transmits decodedbarcode information through a local access point 56 and to the PDSconnected to the hospital network 60. Using a software program, the PDSanalyzes these data and communicates with the patient's record in thehospital EMR 58 to determine if the medication is appropriate for thepatient. For example, the software program may check to see if thepatient is allergic to the medication, if the dosage is correct, or ifthe patient has previously exhibited any detrimental side effects thatmay affect the dosage. In related embodiments, the transceiver may alsoinclude a GUI wherein the clinician enters ancillary information, suchas the dosage of the medication or demographic information describingthe patient, using a ‘soft’ keypad. Or the GUI may include a simplequestionnaire that guides the clinician through the process of checkingthe medication, and then administering it. In still other embodiments,the infusion pump that delivers the medication may include a wirelessconnection through the access point 56 to the PDS 60 or to thetransceiver 72 to automatically supply information related to themedication to the software program.

Once the software program determines that it is safe to administer themedication, it sends a packet from the PDS 60, through the access point56, and back to the transceiver 72, which then renders a GUI instructingthe clinician to proceed. In other embodiments, the PDS 60 sends thepacket through the access point 56 to either a remote computer 62 (e.g.a tablet computer) or a portable device 64 (e.g. a cellular telephone orpersonal digital assistant).

Form Factor of the Body-Worn Monitor

FIGS. 21A and 21B show how the body-worn monitor 100 described aboveattaches to a patient 70 to measure RR, SpO2, cNIBP, and other vitalsigns. These figures show two configurations of the system: FIG. 21Ashows the system used during the indexing portion of the CompositeTechnique, and includes a pneumatic, cuff-based system 85, while FIG.21B shows the system used for subsequent measurements. The indexingmeasurement typically takes about 60 seconds, and is typically performedonce every 4-8 hours. Once the indexing measurement is complete thecuff-based system 85 is typically removed from the patient. Theremainder of the time the monitor 100 performs the RR, HR, SpO2 andcNIBP measurements.

The body-worn monitor 100 features a wrist-worn transceiver 72,described in more detail in FIGS. 22A and 22B, featuring a touch panelinterface 73 that displays the various GUIs described above and in FIG.24. A wrist strap 90 affixes the transceiver 72 to the patient's wristlike a conventional wristwatch. A flexible cable 92 connects thetransceiver 72 to an optical sensor 94 that wraps around the base of thepatient's thumb. During a measurement, the optical sensor 94 generates atime-dependent PPG waveform which is processed along with an ECG tomeasure cNIBP, SpO2, and, in some applications, RR. To determine ACCwaveforms the body-worn monitor 100 features three separateaccelerometers located at different portions on the patient's arm andchest. The first accelerometer is surface-mounted on a circuit board inthe wrist-worn transceiver 72 and measures signals associated withmovement of the patient's wrist. As described above, this motion canalso be indicative of that originating from the patient's fingers, whichwill affect the SpO2 measurement. The second accelerometer is includedin a small bulkhead portion 96 included along the span of the cable 82.During a measurement, a small piece of disposable tape, similar in sizeto a conventional bandaid, affixes the bulkhead portion 96 to thepatient's arm. In this way the bulkhead portion 96 serves twopurposes: 1) it measures a time-dependent ACC waveform from themid-portion of the patient's arm, thereby allowing their posture and armheight to be determined as described in detail above; and 2) it securesthe cable 82 to the patient's arm to increase comfort and performance ofthe body-worn monitor 100, particularly when the patient is ambulatory.The third accelerometer is mounted in the sensor module 74 that connectsthrough cables 80 a-c to ECG electrodes 78 a-c. Signals from thesesensors are then digitized, transmitted through the cable 82 to thewrist-worn transceiver 72, where they are processed with an algorithm asdescribed above to determine RR.

The cuff-based module 85 features a pneumatic system 76 that includes apump, valve, pressure fittings, pressure sensor, manifold,analog-to-digital converter, microcontroller, and rechargeable Li:ionbattery. During an indexing measurement, the pneumatic system 76inflates a disposable cuff 84 and performs two measurements according tothe Composite Technique: 1) it performs an inflation-based measurementof oscillometry and measurement of a corresponding OSC waveform todetermine values for SYS, DIA, and MAP; and 2) it determines apatient-specific relationship between PTT and MAP. These measurementsare described in detail in the co-pending patent application entitled:‘VITAL SIGN MONITOR FOR MEASURING BLOOD PRESSURE USING OPTICAL,ELECTRICAL, AND PRESSURE WAVEFORMS’ (U.S. Ser. No. 12/138,194; filedJun. 12, 2008), the contents of which are incorporated herein byreference.

The cuff 84 within the cuff-based pneumatic system 85 is typicallydisposable and features an internal, airtight bladder that wraps aroundthe patient's bicep to deliver a uniform pressure field. During theindexing measurement, pressure values are digitized by the internalanalog-to-digital converter, and sent through a cable 86 according to aCAN protocol, along with SYS, DIA, and MAP blood pressures, to thewrist-worn transceiver 72 for processing as described above. Once thecuff-based measurement is complete, the cuff-based module 85 is removedfrom the patient's arm and the cable 86 is disconnected from thewrist-worn transceiver 72. cNIBP is then determined using PTT, asdescribed in detail above.

To determine an ECG, the body-worn monitor 100 features a small-scale,three-lead ECG circuit integrated directly into the sensor module 74that terminates an ECG cable 82. The ECG circuit features an integratedcircuit that collects electrical signals from three chest-worn ECGelectrodes 78 a-c connected through cables 80 a-c. As described above,the ECG electrodes 78 a-c are typically disposed in a conventionalEinthoven's Triangle configuration, which is a triangle-like orientationof the electrodes 78 a-c on the patient's chest that features threeunique ECG vectors. From these electrical signals the ECG circuitdetermines up at least three ECG waveforms, each corresponding to aunique ECG vector, which are digitized using an analog-to-digitalconverter mounted proximal to the ECG circuit and sent through the cable82 to the wrist-worn transceiver 72 according to the CAN protocol.There, the ECG and PPG waveforms are processed to determine thepatient's blood pressure. HR and RR are determined directly from the ECGwaveform using known algorithms, such as those described above. Moresophisticated ECG circuits (e.g. five and twelve-lead systems) can pluginto the wrist-worn transceiver to replace the three-lead system shownin FIGS. 21A and 21B.

FIGS. 22A, 22B show three-dimensional views of the wrist-worntransceiver 72 before and after receiving cables 82, 86, 89 from sensorsworn on the patient's upper arm and torso, as well as the cable 92 thatconnects to the optical sensor. The transceiver 72 is sealed in awater-proof plastic casing 117 featuring electrical interconnects (notshown in the figure) on its bottom surface that interface to theterminal ends 111, 119 a-c of cables 82, 86, 89, 92 leading to themonitor's various sensors. The electrical interconnects support serialcommunication through the CAN protocol, described in detail herein,particularly with reference to FIG. 25. During operation, thetransceiver's plastic casing 117 snaps into a plastic housing 106, whichfeatures an opening 109 on one side to receive the terminal end 111 ofthe cable 92 connected to the optical sensor. On the opposing side theplastic housing 106 features three identical openings 104 a-c thatreceive the terminal ends 119 a-c of cables 82, 86, 89 connected to theECG and accelerometer systems (cable 82), the pneumatic cuff-basedsystem (cable 86), and ancillary systems (cable 89) described above. Inaddition to being waterproof, this design facilitates activities such ascleaning and sterilization, as the transceiver contains no openings forfluids common in the hospital, such as water and blood, to flow inside.During a cleaning process the transceiver 72 is simply detached from theplastic housing 106 and then cleaned.

The transceiver 72 attaches to the patient's wrist using a flexiblestrap 90 which threads through two D-ring openings in the plastichousing 106. The strap 90 features mated Velcro patches on each sidethat secure it to the patient's wrist during operation. A touchpaneldisplay 50 renders the various GUIs described above.

The electrical interconnects on the transceiver's bottom side line upwith the openings 104 a-c, and each supports the CAN protocol to relay adigitized data stream to the transceiver's internal CPU, as described indetail with reference to FIG. 25. This allows the CPU to easilyinterpret signals that arrive from the monitor's body-worn sensors, andmeans that these connectors are not associated with a specific cable.Any cable connecting to the transceiver 72 can be plugged into anyopening 104 a-c. As shown in FIG. 22A, the first opening 104 a receivesthe cable 82 that transports digitized ECG waveforms determined from theECG circuit and electrodes, and digitized ACC waveforms measured byaccelerometers in the cable bulkhead and the bulkhead portion associatedwith the ECG cable 82.

The second opening 104 b receives the cable 86 that connects to thepneumatic cuff-based system used for the pressure-dependent indexingmeasurement. This connector receives a time-dependent pressure waveformdelivered by the pneumatic system to the patient's arm, along withvalues for SYS, DIA, and MAP determined during the indexing measurement.The cable 86 unplugs from the opening 104 b once the indexingmeasurement is complete, and is plugged back in after approximately 4-8hours for another indexing measurement.

The final opening 104 c can be used for an auxiliary device, e.g. aglucometer, infusion pump, body-worn insulin pump, ventilator, orend-tidal CO₂ monitoring system. As described with reference to FIG. 25,digital information generated by these systems will include a headerthat indicates their origin so that the CPU can process themaccordingly.

Measuring and Displaying Time-Dependent Physiological Signals

FIGS. 23A and 23B show how a network of sensors 78 a-c, 83, 84, 87, 94within the body-worn monitor 100 connect to a patient 70 to measuretime-dependent ECG 261, PPG 262, OSC 263, ACC 264, and RR 265 waveforms.These, in turn, yield the patient's vital signs and motion parameters.Each waveform 261-265 relates to a unique physiological characteristicof the patient 70. For example, each of the patient's heartbeatsgenerates electrical impulses that pass through the body near the speedof light, along with a pressure wave that propagates through thepatient's vasculature at a significantly slower speed. Immediately afterthe heartbeat, the pressure wave leaves the heart 148 and aorta 149,passes through the subclavian artery 150 to the brachial artery 144, andfrom there through the radial and ulnar arteries 145 to smaller arteriesin the patient's fingers. Three disposable electrodes 78 a-c attached tothe patient's chest measure unique electrical signals which pass to asingle-chip ECG circuit 83 that terminates a distal end of the ECGcable. Typically, these electrodes attach to the patient's chest in aconventional ‘Einthoven's triangle’ configuration featuring three unique‘vectors’, each corresponding to a different lead (e.g. LEAD 1, II, II).Related configurations can also be used when five and twelve-lead ECGsystems are used in place of the three-lead system, as described abovewith reference to FIGS. 21A, 21B. Within the ECG circuit 83 signals areprocessed using an amplifier/filter circuit and analog-to-digitalconverter to generate a digital ECG waveform 261 corresponding to eachlead. The ECG waveform 261 features a sharp, well-defined QRS complexcorresponding to each heartbeat; this marks the initiation of thepatient's cardiac cycle. Heart rate is determined directly from the ECGwaveform 261 using known algorithms, such as those described in thefollowing journal article, the contents of which are incorporated hereinby reference: ‘ECG Beat Detection Using Filter Banks’, Afonso et al.,IEEE Trans. Biomed Eng., 46:192-202 (1999).

To generate an IP waveform 265, one of the ECG electrodes in the circuit78 a is a ‘driven lead’ that injects a small amount of modulated currentinto the patient's torso. A second, non-driven electrode 78 c, typicallylocated on the opposite side of the torso, detects the current, which isfurther modulated by capacitance changes in the patient's chest cavityresulting from breathing. Further processing and filtering of the IPwaveforms 265 yields respiratory rate. Respiration can also bedetermined using an adaptive filtering approach that processes both theIP waveform and ACC waveform 264, as described in more detail in thefollowing co-pending patent application, the contents of which areincorporated herein by reference: BODY-WORN MONITOR FOR MEASURINGRESPIRATION RATE (U.S. Ser. No. 12/559,419, Filed Sep. 14, 2009).

The optical sensor 94 features two LEDs and a single photodetector thatcollectively measure a time-dependent PPG waveform 262 corresponding toeach of the LEDs. The sensor and algorithms for processing the PPGwaveforms are described in detail in the following co-pending patentapplication, the contents of which have been previously incorporatedherein by reference: BODY-WORN PULSE OXIMETER (U.S. Ser. No. 12/559,379;filed Sep. 14, 2009). The waveform 262 represents a time-dependentvolumetric change in vasculature (e.g. arteries and capillaries) that isirradiated with the sensor's optical components. Volumetric changes areinduced by a pressure pulse launched by each heartbeat that travels fromthe heart 148 to arteries and capillaries in the thumb according to theabove-describe arterial pathway. Pressure from the pressure pulse forcesa bolus of blood into this vasculature, causing it to expand andincrease the amount of radiation absorbed, and decrease the transmittedradiation at the photodetector. The pulse shown in the PPG waveform 262therefore represents the inverse of the actual radiation detected at thephotodetector. It follows the QRS complex in the ECG waveform 261,typically by about one to two hundred milliseconds. The temporaldifference between the peak of the QRS complex and the foot of the pulsein the PPG waveform 262 is the PTT, which as described in detail belowis used to determine blood pressure according to the CompositeTechnique. PTT-based measurements made from the thumb yield excellentcorrelation to blood pressure measured with a femoral arterial line.This provides an accurate representation of blood pressure in thecentral regions of the patient's body.

Each accelerometer generates three time-dependent ACC waveforms 264,corresponding to the x, y, and z-axes, which collectively indicate thepatient's motion, posture, and activity level. The body-worn monitor, asdescribed above, features three accelerometers that attach to thepatient: one in the wrist-worn transceiver 72, one in the ECG circuit83, and one near the bicep 87 that is included in the cable connectingthese two components. The frequency and magnitude of change in the shapeof the ACC waveform 264 indicate the type of motion that the patient isundergoing. For example, the waveform 264 can feature a relativelytime-invariant component indicating a period of time when the patient isrelatively still, and a time-variant component when the patient'sactivity level increases. Magnitudes of both components will depend onthe relationship between the accelerometer and a gravity vector, and cantherefore be processed to determine time-invariant features, such asposture and arm height. A frequency-dependent analysis of thetime-variant components yields the type and degree of patient motion.Analysis of ACC waveforms 264 is described in detail in theabove-mentioned patent applications, the contents of which have beenfully incorporated herein by reference.

The OSC waveform 263 is generated from the patient's brachial artery 144with the pneumatic system and a cuff-based sensor 84 during thepressure-dependent portion of the Composite Technique. It represents atime-dependent pressure which is applied to the brachial artery duringinflation and measured by a digital pressure sensor within the pneumaticsystem. The waveform 263 is similar to waveforms measured duringdeflation by conventional oscillometric blood pressure monitors. Duringa measurement, the pressure waveform 263 increases in a mostly linearfashion as pressure applied by the cuff 84 to the brachial artery 144increases. When it reaches a pressure slightly below the patient'sdiastolic pressure, the brachial artery 144 begins to compress,resulting in a series time-dependent pulsations caused by each heartbeatthat couple into the cuff 84. The pulsations modulate the OSC waveform263 with an amplitude that varies in a Gaussian-like distribution, withmaximum modulation occurring when the applied pressure is equivalent tothe patient's MAP. The pulsations can be filtered out and processedusing digital filtering techniques, such as a digital bandpass filterthat passes frequencies ranging from 0.5-20 Hz. The resulting waveformcan be processed to determine SYS, DIA, and MAP, as is described indetail in the above-referenced patent applications, the contents ofwhich have been previously incorporated herein by reference. The cuff 84and pneumatic system are removed from the patient's bicep once thepressure-dependent component of the Composite Technique is complete.

The high-frequency component of the OSC waveform 263 (i.e. the pulses)can be filtered out to estimate the exact pressure applied to thepatient's brachial artery during oscillometry. According to theComposite Technique, PTT measured while pressure is applied willgradually increase as the brachial artery is occluded and blood flow isgradually reduced. The pressure-dependent increase in PTT can be fitwith a model to estimate the patient-specific relationship between PTTand blood pressure. This relationship, along with SYS, MAP, and DIAdetermined from the OSC waveform during inflation-based oscillometry, isused during the Composite Technique's pressure-free measurements todetermine blood pressure directly from PTT.

There are several advantages to making the indexing measurement duringinflation, as opposed to deflation. Measurements made during inflationare relatively fast and comfortable compared to those made duringdeflation. Inflation-based measurements are possible because of theComposite Technique's relatively slow inflation speed (typically 5-10mmHg/second) and the high sensitivity of the pressure sensor used withinthe body sensor. Such a slow inflation speed can be accomplished with asmall pump that is relatively lightweight and power efficient. Moreover,measurements made during inflation can be immediately terminated oncesystolic blood pressure is calculated. This tends to be more comfortablethan conventional cuff-based measurements made during deflation. In thiscase, the cuff typically applies a pressure that far exceeds thepatient's systolic blood pressure; pressure within the cuff then slowlybleeds down below the diastolic pressure to complete the measurement.

A digital temperature sensor proximal to the ECG circuit 83 measures thepatient's skin temperature at their torso. This temperature is anapproximation of the patient's core temperature, and is used mostly forpurposes related to trending and alarms/alerts.

FIG. 24 shows how the above-described ECG, PPG, and IP waveforms, alongwith vital signs calculated from them, are rendered using differentscreens 300, 304, 306, 308 within a GUI. In all cases, the waveforms aredisplayed with a rolling graphical technique, along with a moving barthat indicates the most current point in time. As per the AAMI/ANSIEC-13 reference standard, the ECG waveforms are displayed alongside abar that indicates a signal intensity of 1 mV. Screen 308 showsdifferent ECG vectors (corresponding to, e.g., Lead I, II, III, aVR,aVF) that are rendered when the clinician taps the ECG waveform onscreen 300, and then the corresponding lead on screen 308. Waveforms fora particular vital sign (e.g. a PPG waveform for the SpO2 measurement;an IP waveform for the RR measurement) are rendered when the cliniciantaps on the value of the corresponding vital sign. During a measurementboth waveforms and the vital signs calculated from them are wirelesslytransmitted to the PDS, as described above.

Communicating with Multiple Systems Using the CAN Protocol

As described above, the ECG, ACC, and pneumatic systems within thebody-worn system send digitized information to the wrist-worntransceiver through the CAN protocol. FIG. 25 shows a schematic drawingindicating how CAN packets 201 a-d, 212 a-e transmitted between thesesystems facilitate communication. Specifically, each of the ACC 215, ECG216, pneumatic 220, and auxiliary 245 systems include a separateanalog-to-digital converter, microcontroller, frequency-generatingcrystal oscillator (typically operating at 100 kHz), and real-time clockdivider that collectively generate and transmit digital data packets 201a-d according to the CAN protocol to the wrist-worn transceiver 72. Eachcrystal uses the internal real-time clock on the internal microprocessorwithin the respective system. This allows the microcontroller withineach system to be placed in a low-power state in which its real-timeoperating system (RTOS) dispatch system indicates that it is not readyto run a task. The real-time clock divider is programmed to create aninterrupt which wakes up the microcontroller every 2 milliseconds.

The wrist-worn transceiver 72 features a ‘master clock’ that generatesreal-time clock ‘ticks’ at the sampling rate (typically 500 Hz, or 2 msbetween samples). Each tick represents an incremented sequence number.Every second, the wrist-worn transceiver 72 transmits a packet 212 eover the CAN bus that digitally encodes the sequence number. One of thecriteria for accurate timing is that the time delay between theinterrupt and the transmission of the synchronizing packet 212 e, alongwith the time period associated with the CAN interrupt service routine,is predictable and stable. During initialization, the remote CAN busesdo not sleep; they stay active to listen for the synchronization packet212 e. The interrupt service routine for the synchronization packet 212e then establishes the interval for the next 2 millisecond interruptfrom its on-board, real-time crystal to be synchronized with the timingon the wrist-worn transceiver 72. Offsets for the packet transmissionand interrupt service delays are factored into the setting for thereal-time oscillator to interrupt synchronously with the microprocessoron the wrist-worn transceiver 72. The magnitude of the correction factorto the real-time counter is limited to 25 of the 2 millisecond intervalto ensure stability of this system, which represents a digitalphase-locked loop.

When receipt of the synchronization packet 212 e results in a timingcorrection offset of either a 0, +1, or −1 count on the remote system'soscillator divider, software running on the internal microcontrollerdeclares that the system is phase-locked and synchronized. At thispoint, it begins its power-down operation and enables measurement ofdata as described above.

Each remote system is driven with a 100 kHz clock, and a single count ofthe divider corresponds to 20 microseconds. This is because the clockdivider divides the real-time clock frequency by a factor of 2. This isinherent in the microcontroller to ensure that the clock has a 50% dutycycle, and means the clock can drift +/−20 microseconds before theactual divider chain count will disagree by one count, at which time thesoftware corrects the count to maintain a phase-locked state. There isthus a maximum of 40 microseconds of timing error between datatransmitted from the remote systems over the CAN bus. Blood pressure isthe one vital sign measured with the body-worn monitor that iscalculated from time-dependent waveforms measured from different systems(e.g. PPG and ECG waveforms). For this measurement, the maximum40-microsecond timing error corresponds to an error of +/−0.04 mmHg,which is well within the error (typically +/−5 mmHg) of the measurement.

In order to minimize power consumption, the wrist-worn transceiver 72and remote systems 215, 216, 220, 245 power down their respective CANbus transceivers between data transfers. During a data transfer, eachsystem generates a sequence number based that is included in thesynchronization packet 212 e. The sequence number represents theinterval between data transfers in intervals of 2 milliseconds. It is afactor of 500 (e.g. 2, 4, 5, 10) that is the number of 2 millisecondintervals between transfers on the CAN bus. Each remote system enablesits CAN bus during the appropriate intervals and sends its data. When ithas finished sending its data, it transmits a ‘transmit complete’ packetindicating that the transmission is complete. When a device has receivedthe ‘transmit complete’ packet it can disable its CAN transceiver tofurther reduce power consumption.

Software in each of the ACC 215, ECG 216, pneumatic 220, and auxiliary245 systems receive the sequence packet 212 e and the correspondingsequence number, and set their clocks accordingly. There is typicallysome inherent error in this process due to small frequency differencesin the crystals (from the ideal frequency of 100 kHz) associated witheach system. Typically this error is on the order of microseconds, andhas only a small impact on time-dependent measurements, such as PTT,which are typically several hundred milliseconds.

Once timing on the CAN bus is established using the above-describedprocedure, each of the ACC 215, ECG 216, and pneumatic 220 systemsgenerate time-dependent waveforms that are transmitted in packets 201a-d, each representing an individual sample. Each packet 201 a-dfeatures a header portion which includes the sequence number 212 a-d andan initial value 210 a-d indicating the type of packet that istransmitted. For example, accelerometers used in the body-worn systemare typically three-axis digital accelerometers, and generate waveformsalong the x, y, and z-axes. In this case, the initial value 210 aencodes numerical values that indicate: 1) that the packet contains ACCdata; and 2) the axis (x, y, or z) over which these data are generated.Similarly, the ECG system 216 can generate a time-dependent ECG waveformcorresponding to Lead I, II, or III, each of which represents adifferent vector measured along the patient's torso. Additionally, theECG system 216 can generate processed numerical data, such as heart rate(measured from time increments separating neighboring QRS complexes),respiratory rate (from an internal impedance pneumography component), aswell as alarms calculated from the ECG waveform that indicateproblematic cardiovascular states such as VTAC, VFIB, and PVCs.Additionally, the ECG system can generate error codes indicating, forexample, that one of the ECG leads has fallen off. The ECG systemtypically generates an alarm/alert, as described above, corresponding toboth the error codes and potentially problematic cardiovascular states.In this case, the initial value 210 b encodes numerical values thatindicate: 1) that the packet contains ECG data; 2) the vector (Lead I,II, or III) corresponding to the ECG data; and 3) an indication if acardiovascular state such as VTAC, VFIB, or PVCs was detected.

The pneumatic system 220 is similar to the ECG system in that itgenerates both time-dependent waveforms (i.e. a pressure waveform,measured during oscillometry, characterizing the pressure applied to thearm and subsequent pulsations measured during an oscillometricmeasurement) and calculated vital signs (SYS, DIA, and MAP measuredduring oscillometry). In some cases errors are encountered during theoscillometric blood pressure measurement. These include, for example,situations where blood pressure is not accurately determined, animproper OSC waveform, over-inflation of the cuff, or a measurement thatis terminated before completion. In these cases the pneumatic system 220generates a corresponding error code. For the pneumatic system 220 theinitial value 210 c encodes numerical values that indicate: 1) that thepacket contains blood pressure data; 2) an indication that the packetincludes an error code.

In addition to the initial values 210 a-d, each packet 201 a-d includesa data field 214 a-d that encodes the actual data payload. Examples ofdata included in the data fields 214 a-d are: 1) sampled values of ACC,ECG, and pressure waveforms; 2) calculated heart rate and blood pressurevalues; and 3) specific error codes corresponding to the ACC 215, ECG216, pneumatic 220, and auxiliary 225 systems.

Upon completion of the measurement, the wrist-worn transceiver 72receives all the CAN packets 201 a-d, and synchronizes them in timeaccording to the sequence number 212 a-d and identifier 210 a-d in theinitial portions 216 of each packet. Every second, the CPU updates thetime-dependent waveforms and calculates the patient's vital signs andmotion-related properties, as described above. Typically these valuesare calculated as a ‘rolling average’ with an averaging window rangingfrom 10-20 seconds. The rolling average is typically updated everysecond, resulting in a new value that is displayed on the wrist-worntransceiver 72. Each packet received by the transceiver 72 is alsowirelessly retransmitted as a new packet 201 b′ through a wirelessaccess point 56 and to both an PDS and RVD within a hospital network 60.The new packet 201 b′ includes the same header 210 b′, 212 b′ and datafield information 214 b′ as the CAN packets transmitted between systemswithin the body-worn monitor. Also transmitted are additional packetsencoding the cNIBP, SpO2, and processed motion states (e.g. posture,activity level, degree of motion), which unlike heart rate and SYS, DIA,and MAP are calculated by the CPU in the wrist-worn transceiver. Uponreceipt of the packet 201 b′, the RVD displays vital signs, waveforms,motion information, and alarms/alerts, typically with a large monitorthat is easily viewed by a clinician. Additionally the PDS can sendinformation through the hospital network (e.g. in the case of analarm/alert), store information in an internal database, and transfer itto a hospital EMR.

Alternate IT Configurations

FIG. 26 shows an alternate configuration of the invention wherein thetransceiver 72 transmits both voice and data information through awireless access point 56A and to the Internet 55, and from there to thehospital network and PDS 60. Such a configuration would be used, forexample, when the patient is located outside of the hospital (e.g. athome). It allows clinicians to monitor and care for a patient as if theywere located in the hospital. Once information arrives at the PDS 60, itcan be transferred to the hospital EMR system 58, or through a wirelessaccess point 56B within the hospital to an external computer 62 or aportable device 64.

In an alternate embodiment, as shown in FIG. 27, the first wirelessaccess point 56A shown in FIG. 26 is replaced by a wireless modem 64A,such as a cellular telephone or personal digital assistant. Here, thewireless modem 64A receives voice and data information from thetransceiver through a peer-to-peer wireless interface (e.g. an interfacebased on 802.11b/g or 802.15.4). The wireless modem 64A then transmitsthe voice and data information to the Internet 55 using, e.g., acellular connection, such as one based on GSM or CDMA. In yet anotherembodiment, as shown in FIG. 28, the transceiver 72 includes an internallong-range wireless transmitter based on a cellular protocol (e.g. GSMor CDMA), allowing it to transmit voice and data information directly tothe Internet 55. In the embodiments shown in both FIGS. 27 and 28,information sent through the Internet is ultimately received by the PDS60, and is sent from there through a wireless access point 56 to eitherthe remote computer 62 or portable device 64.

In embodiments, the transceiver 72 features multiple wirelesstransmitters, and can operate in multiple modes, such as each of thoseshown in FIGS. 26-28. In this case the wireless protocol (based on, e.g.802.11 or cellular) is manually selected using the GUI, or automaticallyselected based on the strength of the ambient wireless signal.

Other Embodiments of the Invention

In addition to those methods described above, the body-worn monitor canuse a number of additional methods to calculate blood pressure and otherproperties from the optical and electrical waveforms. These aredescribed in the following co-pending patent applications, the contentsof which are incorporated herein by reference: 1) CUFFLESSBLOOD-PRESSURE MONITOR AND ACCOMPANYING WIRELESS, INTERNET-BASED SYSTEM(U.S. Ser. No. 10/709,015; filed Apr. 7, 2004); 2) CUFFLESS SYSTEM FORMEASURING BLOOD PRESSURE (U.S. Ser. No. 10/709,014; filed Apr. 7, 2004);3) CUFFLESS BLOOD PRESSURE MONITOR AND ACCOMPANYING WEB SERVICESINTERFACE (U.S. Ser. No. 10/810,237; filed Mar. 26, 2004); 4) BILATERALDEVICE, SYSTEM AND METHOD FOR MONITORING VITAL SIGNS (U.S. Ser. No.11/420,774; filed May 27, 2006); 5) CUFFLESS BLOOD PRESSURE MONITOR ANDACCOMPANYING WIRELESS MOBILE DEVICE (U.S. Ser. No. 10/967,511; filedOct. 18, 2004); 6) BLOOD PRESSURE MONITORING DEVICE FEATURING ACALIBRATION-BASED ANALYSIS (U.S. Ser. No. 10/967,610; filed Oct. 18,2004); 7) PERSONAL COMPUTER-BASED VITAL SIGN MONITOR (U.S. Ser. No.10/906,342; filed Feb. 15, 2005); 8) PATCH SENSOR FOR MEASURING BLOODPRESSURE WITHOUT A CUFF (U.S. Ser. No. 10/906,315; filed Feb. 14, 2005);9) PATCH SENSOR FOR MEASURING VITAL SIGNS (U.S. Ser. No. 11/160,957;filed Jul. 18, 2005); 10) WIRELESS, INTERNET-BASED SYSTEM FOR MEASURINGVITAL SIGNS FROM A PLURALITY OF PATIENTS IN A HOSPITAL OR MEDICAL CLINIC(U.S. Ser. No. 11/162,719; filed Sep. 9, 2005); 11) HAND-HELD MONITORFOR MEASURING VITAL SIGNS (U.S. Ser. No. 11/162,742; filed Sep. 21,2005); 12) CHEST STRAP FOR MEASURING VITAL SIGNS (U.S. Ser. No.11/306,243; filed Dec. 20, 2005); 13) SYSTEM FOR MEASURING VITAL SIGNSUSING AN OPTICAL MODULE FEATURING A GREEN LIGHT SOURCE (U.S. Ser. No.11/307,375; filed Feb. 3, 2006); 14) BILATERAL DEVICE, SYSTEM AND METHODFOR MONITORING VITAL SIGNS (U.S. Ser. No. 11/420,281; filed May 25,2006); 15) SYSTEM FOR MEASURING VITAL SIGNS USING BILATERAL PULSETRANSIT TIME (U.S. Ser. No. 11/420,652; filed May 26, 2006); 16) BLOODPRESSURE MONITOR (U.S. Ser. No. 11/530,076; filed Sep. 8, 2006); 17)TWO-PART PATCH SENSOR FOR MONITORING VITAL SIGNS (U.S. Ser. No.11/558,538; filed Nov. 10, 2006); and, 18) MONITOR FOR MEASURING VITALSIGNS AND RENDERING VIDEO IMAGES (U.S. Ser. No. 11/682,177; filed Mar.5, 2007).

Other embodiments are also within the scope of the invention. Forexample, other measurement techniques, such as conventional oscillometrymeasured during deflation, can be used to determine SYS, DIA, and MAPfor the above-described algorithms. Additionally, processing units andprobes for measuring pulse oximetry similar to those described above canbe modified and worn on other portions of the patient's body. Forexample, optical sensors with finger-ring configurations can be worn onfingers other than the thumb. Or they can be modified to attach to otherconventional sites for measuring SpO2, such as the ear, forehead, andbridge of the nose. In these embodiments the processing unit can be wornin places other than the wrist, such as around the neck (and supported,e.g., by a lanyard) or on the patient's waist (supported, e.g., by aclip that attaches to the patient's belt). In still other embodimentsthe probe and processing unit are integrated into a single unit.

In embodiments, the interface rendered on the display at the centralnursing station features a field that displays a map corresponding to anarea with multiple sections. Each section corresponds to the location ofthe patient and includes, e.g., the patient's vital signs, motionparameter, and alarm parameter. For example, the field can display a mapcorresponding to an area of a hospital (e.g. a hospital bay or emergencyroom), with each section corresponding to a specific bed, chair, orgeneral location in the area.

Further embodiments of the invention are within the scope of thefollowing claims:

What is claimed is:
 1. A method for monitoring a patient, comprising thefollowing steps: (a) contacting at least one of a display device and anarea proximal to the display device with a patient monitor comprising amotion sensor, the contacting causing the motion sensor to generate amotion-signal, wherein the motion signal is a time-dependent waveformcomprising a pulse; (b) transmitting the motion signal to a remotecomputer; (c) transmitting the location of the patient monitor to theremote computer; (d) processing the motion signal and the location ofthe patient monitor with the remote computer to determine the locationof the display device, and to associate the patient monitor with thedisplay device; and (e) measuring at least one set of vital signinformation with the patient monitor and displaying the vital signinformation on the display device.
 2. The method of claim 1, wherein themotion sensor comprises an accelerometer.
 3. The method of claim 1,wherein the patient monitor further comprises a wireless transmitter. 4.The method of claim 3, wherein the wireless transmitter is configured tooperate on a wireless network.
 5. The method of claim 4, wherein thestep for determining the location of the display device furthercomprises analyzing signals characterizing a signal strength betweenmultiple access points operating on the wireless network and thewireless transmitter.
 6. The method of claim 4, wherein the computer isa remote computer configured to receive signals from the patient monitorthrough the wireless transmitter.
 7. The method of claim 6, wherein thedisplay device is configured to receive signals from the remote computerthrough the network.
 8. The method of claim 5, wherein the step fordetermining the location of the display device further comprisestriangulating at least three values of signal strength, with each valueof signal strength characterizing a signal between an individual accesspoint operating on the wireless network and the wireless transmitter. 9.The method of claim 8, wherein the step for determining the location ofthe display device further comprises comparing an approximate locationvalue determined by triangulating the at least three values of signalstrength with a map grid.
 10. The method of claim 9, wherein the mapgrid comprises a true location value of the display device.
 11. Themethod of claim 10, wherein the step for determining the location of thedisplay device further comprises comparing an approximate location valuethat is proximal to a true location value comprised by the map grid. 12.The method of claim 10, wherein the step for determining the location ofthe display device further comprises comparing an approximate locationvalue to a true location value within a pre-determined radius.
 13. Themethod of claim 12, wherein the pre-determined radius is between 1-5 m.14. A method for monitoring a patient, comprising the following steps:(a) contacting at least one of a display device and an area proximal tothe display device with a patient monitor comprising a motion sensor anda wireless transmitter, the contacting causing the motion sensor togenerate a motion signal, wherein the motion signal is a time-dependentwaveform comprising a pulse; (b) wirelessly transmitting the motionsignal from the patient monitor to a remote computer over a wirelessnetwork using the wireless transmitter; (c) processing wireless signalsreceived by multiple wireless access points on the wireless network todetermine an approximate location of the patient monitor andtransmitting the approximate location of the patient monitor to theremote computer; (d) processing the motion signal and the approximatelocation of the patient monitor to determine the location the displaydevice, and associate the patient monitor with the display device; (e)measuring at least one, set of vital sign information from the patientwith the patient monitor; and (f) displaying the at least one set ofvital sign information on the display device.